On Variation and Some of its Sources

Diversity

Virtually every component is made to be assembled with its counterpart(s) into sub-assemblies and final assemblies.

If individual pieces of a given component could be made identical to one another, then they would either all conform or all fail to conform to the component’s design requirements. If they conform, then we could pick a piece at random for use in a sub- or final-assembly. It would fit and function without fail, as intended.

But material varies, machine operation varies, the work method varies, workers vary, measurement varies, as does the environment. Such variation, especially in combination, makes it impossible to produce anything identical. Variation is a fundamental principle of nature. All things vary.

Variation affects the fit, the form and the function of a component. And, it is propagated along the assembly line such that the final product is at times a mixed bag of conforming and nonconforming widgets.

Material Consider 316 Stainless Steel. It is used to make medical devices. Manufacturers buy it from metal producers in sheet stock or bar stock.

If we measured the dimensional attributes of the received stock, e.g. its diameter or length, for several different purchase orders, we would see that they were not identical between orders. They vary. If we measured these attributes for pieces received in a single order, we would see that they were not identical between pieces of that order either. If we measured these attributes for a single piece at different points in its cross-section, we would see that they, too, were not identical. If we then zoomed in to investigate the crystalline structure of the stainless steel, we would see that the crystals were not identical in shape or size.

The elemental composition, in percent by weight, of 316 Stainless Steel is: 0.08% Carbon, 2.00% Manganese, 0.75% Silicon, 16.00-18.00% Chromium, 10.00-14.00% Nickel, 2.00-3.00% Molybdenum, 0.045% Phosphorous, 0.030% Sulfur, 0.10% Nitrogen, and the balance is Iron. We see that the amount of Chromium, Nickel, Molybdenum and Iron are specified as ranges i.e. they are expected to vary within them by design!

These are some of the ways a specific raw material used in the production of medical devices varies. Keep in mind that a medical device isn’t a single component but an assembly of several components likely made of different materials that will vary in just such ways as well. All this variation affects the processing (i.e. machining, cleaning, passivation, etc.) of the material during manufacturing, as well as the device performance in use.

Machine One piece of equipment used in the production of medical device components is the CNC (Computer Numerical Control) machine. Its condition, as with all production equipment, varies with use.

Take the quality of the lubricating fluid: it changes properties (e.g. its viscosity) with temperature thus affecting its effectiveness. The sharpness of the cutting tool deteriorates with use. A component made with a brand new cutting tool will not be identical to one made from a used cutting tool whose cutting edges have dulled. The cutting is also affected by both the feed-rate and the rotation-rate of the cutting tool. Neither of which remain perfectly constant at a particular setting.

What’s more, no two machines perform in identical ways even when they are the same make and model made by the same manufacturer. In use, they will almost never be in the same state as each other, with one being used more or less than the other, and consumables like cutting tools in different states of wear. Such variability will contribute to the variability between the individual pieces of the component.

Method Unless there is standardized work, we would all do the work in the best way we know how. Each worker will have a best way slightly different from another. Variation in best ways will find its way into the pieces made using them.

These days a production tool like a CNC machine offers customized operation. The user can specify the settings for a large number of operating parameters. Users write “code” or develop a “recipe” that specifies the settings for various operating parameters in order to make a particular component. If several such pieces of code or recipes exist, one different from another, and they are used to make a particular component, they will produce pieces of that component that vary from one to another.

When and how an adjustment is made to control parameters of a tool will affect the degree of variation between one piece and another. Consider the method where a worker makes adjustment(s) after each piece is made to account for its deviation from the target versus one where a worker makes an adjustment only when a process shift is detected. Dr. Deming and Dr. Wheeler have shown that tampering with a stable process, as the first worker does, will serve to increase the variation in the process.

All such variation in method will introduce variability into the manufactured pieces.

Man There are a great many ways in which humans vary physically from one another. Some workers are men, others are women. Some are short, others are tall. Some are young, others are older. Some have short fat fingers, others have long thin fingers. Some have great eyesight, others need vision correction. Some have great hearing, others need hearing aids. Some are right handed, others are left handed. Some are strong, others not so much. Some have great hand-eye coordination, others do not. We all come from diverse ethnic backgrounds.

Not all workers have identical knowledge. Some have multiple degrees, others are high school graduates. Some have long experience doing a job, others are fresh out of school. Some have strong knowledge in a particular subject, others do not. Some have deep experience in a single task, others have shallow experience. Some have broad experience, others have focused experience.

Last, but not least, we all bring varying mindsets to work. Some may be intrinsically motivated, others need to be motivated externally. Some may be optimists, others may be pessimists. Some want to get better everyday, others are happy where they are. Some like change, others resist it. Some are data driven, others use their instinct.

All this variation affects the way a job gets done. The variation is propagated into the work and ultimately manifests itself in the variation of the manufactured component.

Measurement We consider a measured value as fact, immutable. But that’s not true. Measuring the same attribute repeatedly does not produce identical results between measurements.

Just like production tools, measurement tools wear from use. This affects the measurement made with it over the course of its use.

And also just like production tools, the method (e.g. how a part is oriented, where on the part the measurement is made, etc.) used to make a measurement affects the measured value. There is no true value of any measured attribute. Different measurement methods produce different measurements of the same attribute.

So even if by chance two pieces were made identical we wouldn’t be able to tell because of the variability inherent in the measurement process.

Environment Certain environmental factors affect all operations regardless of industry. One of them is time. It is not identical from one period to the next. Months in a year are not identical in duration. Seasons in a year are different from one another. Daytime and nighttime are not identical to one another. Weekdays and weekends are not identical to one another.

Even in a climate controlled facility the temperature cycles periodically around a target. It varies between locations as well. Lighting changes over the course of the day. Certain parts of the workplace may be darker than others. Noise, too, changes over the course of the day: quiet early in the morning or into the night, and noisier later into the day. There is variation in the type of noise, as well. Vibration by definition is variation. It can come from a heavy truck rolling down the street or the motor spinning the cutting tool in a production machine. Air movement or circulation isn’t the same under a vent as compared to a spot away from a vent, or when the system is on versus when it is off.

The 5M+E (Material, Machine, Method, Man, Measurement, and Environment) is just one way to categorize sources of variation. The examples in each are just a few of the different sources of variation that can affect the quality of individual pieces of a component. While we cannot eliminate variation, it is possible to systematically reduce it and achieve greater and greater uniformity in the output of a process. The objective of a business is to match the Voice of the Customer (VOC) and the Voice of the Process (VOP). The modern day world-class definition of quality is run-to-target with minimal variation!

Our approach has been to investigate one by one the causes of various “unnecessaries” in manufacturing operations…
— Taiichi Ohno describing the development of the Toyota Production System

Links
[1] Kume, Hitoshi. Statistical Methods for Quality Improvement. Tokyo, Japan: The Association for Overseas Technical Scholarship. 2000. Print. ISBN 4-906224-34-2

[2] Monden, Yasuhiro. Toyota Production System. Norcross, GA: Industrial Engineering and Management Press. 1983. Print. ISBN 0-89806-034-6

[3] Wheeler, Donald J. and David S. Chambers. Understanding Statistical Process Control. Knoxville, TN: SPC Press, Inc. 1986. Print. ISBN 0-945320-01-9

Some Thoughts on the Toyota Production System

Murmuration

The Toyota production system (TPS) was not designed.

The technique we call the Toyota production system was born through our various efforts to catch up with the automotive industries of western advanced nations…
— Taiichi Ohno, Foreword to Toyota Production System[1]

It grew out of “various efforts.” Often these efforts were “trial and error.” Experiments were run, lots of them. Some yielded desirable results, others did not. But lessons could be learned from every experiment—What worked? What didn’t? Why?

What made an outcome of an experiment desirable? What was the purpose of these efforts?

Above all, one of our most important purposes was increased productivity and reduced costs.

So how was productivity increased and costs reduced? Toyota guessed (or hypothesized) this could be done by “eliminating all kinds of unnecessary functions in the factories,” what we’ve come to term as waste. We all recognize there are many ways to produce the same result. However, some are less wasteful than others. They are efficient.

By attending to what is actually happening, by observing the real process, a worker could identify waste in various forms. Observation comes before understanding.

Our approach has been to investigate one by one the causes of various “unnecessaries” in manufacturing operations…

One by one!

If we take a minute to think about how many different operations—small and large, localized and cross-functional—take place in factories, we start to understand the scale of Toyota’s effort. That takes patience, discipline and perseverance i.e. grit. The image of a bee hive or a migrating wildebeest herd or a flock of starlings comes to my mind. There is no centralized design or control, nevertheless all members work with the same purpose.

…and to devise methods for their solution…

To eliminate the causes of different types of waste, i.e. the unnecessary functions in the factories, Toyota devised solutions such as kanban, just-in-time, production smoothing, and autonomation. These methods are outcomes of a way of thinking and being. Experimentation through trial and error. They are the means Toyota developed to achieve its purpose of increasing productivity and reducing costs. They could be spread within Toyota, but can they be used elsewhere? Many examples exist of attempts to incorporate them in companies here in the West. I’ve had a front row seat to many of them. Few, if any, show the type of sustained benefits seen by Toyota. Why is that? Context!

Although we have a slight doubt whether our Just-in-time system could be applied to the foreign countries where business climates, industrial relations, and many other social systems are different from ours, we firmly believe there is no significant difference among the final purposes of the firms and the people working in them.

All companies operate within an environment: business climates (e.g. the regulatory environment), industrial relations (i.e. how companies relate to their peers and their suppliers, their communities, and the natural environment), and social systems (such as local traditions and customs). These will necessarily affect the type and form of tools that emerge from experiments that (should) happen in support of a particular company’s purpose. By the way, contrary to Ohno’s point, and as irrational as it seems, not all companies have the same final purpose as Toyota—to increase productivity and reduce costs. Similarly, people in the West have different objectives, different worldviews, than those in the East.

The Toyota production system, and perhaps even lean, is a way of being in pursuit of certain purpose(s). They are not a set of tools to copy and deploy independent of and indifferent to the context where they are deployed. It shouldn’t surprise anyone that efforts to unthinkingly copy and apply them fail more often than succeed.

Links
[1] Monden, Yasuhiro. Toyota Production System. Norcross, GA: Industrial Engineering and Management Press. 1983. Print. ISBN 0-89806-034-6

Buddhism as Dialogue — Alan Watts

I was discussing last night the bodhisattva doctrine in Mahayana Buddhism and comparing it, or relating it to the two great tendencies in Indian spirituality: anti-worldliness, or other worldliness, and world affirmation, and showing how the idea that the highest kind of a Buddha is in a certain way a non-Buddha. The highest kind of a Buddha is like an ordinary person. And this comes out very very much in various tendencies in Zen where, for example, all the painting peculiarly characteristic of Zen Buddhism in Chinese and Japanese tradition is, as it were, secular. It has a peculiarly non-religious atmosphere. That is to say the painting of Shingon sect and Tendai sect, as you saw it in the museum today, was religious painting. You could tell at once that the subject matter of these paintings is religious. But with Zen painting the way of dealing with philosophical or spiritual themes is secular.

So that when an artist like Sengai[1][2], living in the 17th century Japan, paints the Buddha there is something slightly humorous about the Buddha. He wears his halo over one ear. There is an informality; a slight raffishness. And so this comes from China, from those great Sung artists like Liang Kai[3][4] who painted the sixth patriarch of Zen chopping bamboos looking like the most extraordinarily unkempt country oaf. So, also, the greatest Zen painting has as its subject matter not really religious themes at all. It uses pine branches, rocks, bamboos, grasses, everything of that kind. And you would never know that these things were icons. Likewise also in poetry which we will go into more extensively in the future. The superb expression of Zen poetry is derived from the Chinese poet Ho Koji who says:

Wondrous action
Supernatural power
Drawing water
Carrying fuel

Now that’s…that poem is a little bit too religious for Zen taste. And so preferable to that is Basho’s famous poem:

The old pond
A frog jumps in
Plop

Plop is the only possible English translation for the Japanese mizu no oto, which means literally the water’s sound—plop. That poem you see is very high style Zen poem because it has nothing in it about religion. There is a poem on the edge which also was written by Basho which says:

When the lightning flashes
How admirable he who does not think life is fleeting

You see, the flash of a lightning is a Buddhist cliché for the transiency of the world. Your life goes by and disappears as fast as a flash of lightning. That becomes a cliché. So all religion, all religious comments about life eventually become clichés. Religion is always falling apart and becoming a certain kind of going through the motions. A kind of imitation of attitudes as if one would…say we’ve got a book called The Imitation of Christ (it’s a terrible book), because everybody who imitates Christ is a kind of a fake Jesus. So in the same way there’s all kinds of imitation Buddhas. Not just sitting on altars made of wood…gilded, but just sitting around in monasteries. So one might say then that the highest kind of religious or spiritual attainment has no no sign about it that it is religious or that it is spiritual. And so as a metaphor for this there was used in Buddhism from the very beginning the idea of the tracks of birds in the sky. They don’t leave any tracks. And so the way of the enlightened man is like a track of a bird in the sky. And as one poem, a Chinese poem, says:

Entering the forest, he does not disturb a blade of grass
Entering the water, he does not make a ripple

In other words, there is no sign about him to indicate that he is self consciously religious. And this goes, too, for the fact that his not having any religious sign is also not something contrived. It isn’t like Protestant simplicity. You know all those Catholics with their rituals and how dreadful and insincere that is. The real reason you know why Protestants think Catholic ritual is insincere? You know? It’s expensive. Protestantism started in the Burgher cities of Europe—places like Freiburg, Hamburg, you know, and Geneva—because the merchant class, who were the foundation of the bourgeoisie, got annoyed, because every time a saint’s day came around, all their employees got a day of, because it was a holy day and they had to attend mass. There were so many of these nuisance holy days and all these contributions that were assessed by the Church: buying your way out of Purgatory and saying masses for the dead and so on and so forth, they found this not very economical. The priests were getting the money instead of the merchants. And so they decried as unbiblical and irreligious and wasteful all the finery of the Catholic religion and wanted something plain and simple. So it became in course of time a sign of being really religious to avoid rituals and to avoid colorful clothing and splendor in churches and to be as ordinary as possible. But that is not yet the real religion, of giving no sign of having a religion, because this simplicity and absence of ritual itself becomes a sign; a way of advertising how spiritual you are.

So the completely bodhisattva type of person doesn’t leave any track either by being religious overtly or by non-religious overtly. How will you be neither religious nor non-religious? See, that’s the great test. How will you avoid that trap of being one or the other? It’s like are you a theist or are you an atheist? See the theist is caught by god and the idea of god, the belief in god. But the atheist is equally caught. Because an atheist is very often an atheist because he cannot stand the idea that god is watching him all the time. That there is this constant all seeing eye prying on your most private life, and that there is this…You know how when you were a child in school and you’re writing something or doing arithmetic and the teacher walks around the class and looks over your shoulder. Nobody wants to be watched like that. Even someone who is good at writing or at arithmetic doesn’t want someone looking over their shoulder while they’re doing it. It puts you off. It bugs you. So the idea of the lord god who is watching us all the time; who is judging everything that we do puts people off, and they can’t stand it. So better be an atheist to get rid of teacher. So…But the atheist, you see, the man who advertises his disbelief in god is a very pious person. Nobody believes in god like an atheist. “There is no god, and I am his prophet.”

So then, the true bodhisattva state is very difficult to pin down as being either…neither supremely religious nor blatantly secular. And people who think that the height of Buddhism or height of Zen is to be perfectly ordinary have still missed the point, like the atheist has missed the point. But, for this reason then there is an element in the art, the painting, the poetry, etc. which has been inspired by this kind of Buddhism; this kind of art where the subject matter is non-religious nevertheless there is something about the way in which this non-religious subject matter is handled that stops you, and you know there’s something strange about it. This is how I first became interested in Oriental philosophy and all that kind of thing. I had an absolute fascination for Chinese and Japanese painting—the secular painting: the landscapes, the treatment of flowers, and grasses and bamboos. There was something about it that struck me as astonishing even though the subject matter was extremely ordinary. And I just, as a child practically, I had to find out what was this strange element in those bamboos, and those grasses. I was being, of course, taught by those painters to see grass. But there was something in there that one could never pin down, never put your finger on it. And that was this thing that I will call the religion of no religion. The supreme attainment of being a Buddha who can’t be detected; who, in this sense then, leaves no trace. You remember, some of you have seen those ten paintings called “The Ten Stages of Spiritual Ox Herding”. And the author…there are two sets of these paintings. There is a heterodox one and an orthodox one. The heterodox one has the…as the man catches the ox it gets progressively whiter until in the end it disappears altogether and the last picture is an empty circle. But the orthodox set of paintings doesn’t end with the empty circle. That…the empty circle arises two from the end; three from the end. It is followed by two others. After the man has attained the state of emptiness, the state in other words of complete iconoclasm, the state of of no attachment to any spiritual or psychological or moral crutch, there are two more steps. One is called “Returning to the Origin” which is represented by a tree beside a stream. And the final one called “Entering the City with Hands Hanging Down.” That means hands…giving a handout, as it were; giving bounty. And it shows a picture of the fat Buddha, Pu Tai, or in Japanese known as Ho Tei, who has an enormous belly, big ears; who carries around a colossal bag. And what do you think this bag has in it? Trash! Wonderful trash. Everything that children love. Things that everybody else has thrown away and thought of as valueless, this bum collects and gives it away to children. And so it says here that “he goes on his way without following the steps of the ancient sages. His door is closed,” that’s the door of his house, “and no glimpses of his interior life are to be seen.” So, in other words, it’s like when you erect a building, while you’re building it, you have all kinds of scaffolding up. That shows you that building is going on. But when the building is complete the scaffolding is taken down. To open a door, as they say in Zen, you may need to pick up a brick to knock at the door. But when the door is opened you don’t carry the brick inside. To cross a river you need a boat. But when you reach the other side you don’t pick up the boat and carry it. So the brick, the boat, the scaffolding, all these things represent some sort of religious technology or method. And in the end these are all to disappear. So that the saint will not be found in church. I…don’t take what I say literally. The saint can perfectly go to church without being sullied by church. But ordinary people when they go to church they come out stinking of religion.

There was a great Zen master once. And one of his disciples asked him “How am I making progress?” He said, “You’re alright, but you have a trivial fault.” “Well, what is that?” He said, “You have too much Zen.” “Well,” he said, “when you’re studying Zen don’t you think it’s very natural to be talking about it?” The master said, “When it’s like an ordinary conversation it is much better.” And so another monk who was standing by listening to this exchange said to the master, “Why do so specially dislike talking about Zen?” And he replied, “Because it turns ones stomach.”

So what did he mean when he said “when it’s like an ordinary everyday conversation it is somewhat better”? When the old master Jo Shu was asked: at the end of the kalpa when everything is destroyed in fire there will be one thing remaining. What is that? And Jo Shu replied, “It’s windy again this morning.”

So in Zen when you’re asked a question about religion you reply in terms of the secular. When you’re asked about something secular you reply in terms of religion.
So, “What is the eternal nature of the self?” “It’s windy again this morning.”

“Please pass me a knife.” The master hands him the knife with the blade first. “Please give me the other end.” “What would you do with the other end?” See? Here the disciple starts out with the ordinary–”please pass me the knife.” And suddenly he finds himself involved in a metaphysical problem. But if he starts out with the metaphysical he’s going to get involved with the knife.

So, now to go deeply into the religion of non-religion we have to understand the…what you might call the final ultimate attainment of Mahayana Buddhist philosophy. And this is contained in a school of thought which is called in Chinese Huayan, and in Japanese Kegon. Kegon is the intellectual foundation for Zen. And there was a great Chinese master by the name of Shumitsu, who was simultaneously a Zen master, and the fifth patriarch of the Huayan sect. Hua, mean flower; yan, garland: the garland of flowers. And it’s all based on a Sanskrit sutra called Avatamsaka. This is called simply the, in Japanese, Kegon Kyo; a very big sutra. And the subject matter of this sutra are what are called the four dharma worlds. And I must explain what these four worlds are so that you get the point.

First of all there is a level of being which we will call Ji. The word Ji, which is Japanese way of pronouncing the Chinese Chr, is the world of things and events. What you might call the common sense world; the everyday world that our senses normally record. This…the word Ji, the character in Chinese, has a multiplicity of meanings because it can mean a thing or an event. It can also mean business; an affair—not in a love affair, but something in the way the French say les affaire for business. Something important. It can also mean affectation; putting something on or showing off. And so a person who is a master in Zen is called Bu Ji, which means no business, no affectation, nothing special. The poem says:

On Mount Lu there is misty rain
And the river Jiang is at high tide
When you have not been there your heart is filled with longing
But when you have been there and come back it was nothing special
Misty rain on Mount Lu
River Jiang at high tide

But this nothing special is not a way of putting something down. Do you see that? I could say, “Well, it was nothing special. It didn’t really amount to anything.” That’s one way of saying it was very ordinary. Bu Ji, just as it doesn’t mean it was very ordinary in the same way that the person who has no religion is really the most religious, if you see. He’s not just a common ignorant moron. He looks like one, but he isn’t. And you have to know what he knows in order to see that he isn’t and to recognize him for what he is. So nothing special, Bu Ji. It doesn’t stand out. It doesn’t, as we would say, it doesn’t stick out like a sore thumb. So the world of Ji then means generally the world of particulars; the world of multiplicity; the world we ordinarily feel we’re involved in. So that’s the first world.

The second world is called the world of Ri. Now Ri, in Chinese Li, is as I explained to you when we were discussing the idea of the law of nature. The character means the markings in jade, or the grain in wood, or the fiber in muscle. But in the Huayan philosophy the world Ri means the universal underlying all particulars. The one underlying all multiplicity. The unitive principle as distinct from Ji which is the differentiation principle.

So as it were like…it’s like this: when you see into the nature of this world you start from Ji. You start from noticing all the particular things and being baffled by their multiplicity and dealing with the multiplicity of things. But as you go into this you discover… as you understand things…What do you mean when you understand things? It means you become aware of their relationships to each other, and eventually you see the unity behind them. And it is as if the multiplicity of the world dissolved into unity.

So here you encounter a problem. I can see the world as a unity. I can see the world as a multiplicity. But how the devil am I going to put the two visions together.

If I’m to be a practical success in business, in family life, and so on, I have to observe the world of particulars. It’s particulars that matter. I have to know chalk from cheese. But if I become a saint, a monk, or a hermit, then I can…or even perhaps a poet or an artist, I will forget about the practical matters and contemplate the unity; the secret meaning underlying all events. But then every…all those practical people are going to say to me, “You’re…you’re falling down on the job,” you’ve escaped from life, because they feel that the world of particulars is the real world. But the other guy says, “No. Your particulars are not real. You make a success of things, yes, but it’s completely temporary. You think you’re an important person, that you’re really contributing to human life. But actually your success in doing this sort of thing lasts for a few years and then you fall apart like everybody else does. Where’s your success now, when you’re dead? What happened to the millions of dollars you made? Where are you? You’re all gone. So that isn’t real,” from the standpoint of the person who concentrates on the unity.

So then to perfect our understanding we have to go to the third of these worlds which is called Ri-Ji-Mu-Ge. Now that means between Ri: the unity, and Ji: the particulars, Mu: there is no, Ge: block. That means the world of the universal and the world of particulars are not incompatible. Let’s take two very different things and see how they can be united. Take shape and color. Never in a million years can you with a black pencil that can draw shapes make red. But if you have red you can draw a circle. You can draw a red circle even though the circle shape and the red color will never be the same. Yet red circle, they go beautifully together. So think of circle as Ji and red as Ri. The circle is the particular, the color is the universal. They go together.

So then we might say the properly rounded out person is both spiritual and material; both other worldly and worldly. This is the supreme attainment of a human being: to be both. Don’t get one sided. A person who is, what you might call, just a materialist ends up by being very boring. It’s…you know you can live the successful life of the world, and you can own every kind of material refinement: you can have the most beautiful home, delicious food, marvelous yachts and cars and everything. But if you have no touch mysticism, it eventually is all perfectly boring, and you would get tired of it. The on the other hand there are people who are purely spiritual, and they live in a kind of dry world where all luxury has been scrubbed away. And they are very intense people. When you’re in their presence…a very spiritual person, an excessively spiritual person, you feel inclined to sit on the edge of your chair, you are not at ease because you know the eye of judgment is looking through you and going down into your very soul and finding that you’re just a scalawag after all. And here’s this absolutely sincere, this dreadfully honest and unselfish person. This is something which is always puzzling to people brought up in a western environment because great spiritual people are often very very sensuous because they can’t be materialist in the ordinary sense; they can’t be straight open sensuous because for them the world is too wonderful for that; any human being is too marvelous to be treated as just a kind of sexual object. They may be very much a sexual object but so marvelous you have to stop with it and really go into the whole of that marvelous wonderful personality.

So there is a trouble, keeps coming up for the West. When you go to church and you suddenly go to a church where there is a marvelous clergyman and you think he is the very exemplar of life and you idealize him. And then suddenly there develops a frightful scandal that he has an affair with his secretary. And you think all is lost; that the faith has been sold out; that everything is going to wrack and ruin, because he was not purely spiritual. And he himself may be terribly confused and worried about this. Because in our world, you see, we make the spiritual and the material mutually exclusive. But Ri-Ji-Mu-Ge, this third world means that between the spiritual and the material there is no obstruction. So we might say this would sound as if it were the highest level, but its one more to come which is called Ji-Ji-Mu-Ge. This means then suddenly Ri has disappeared. But between Ji and Ji there is no obstruction. Between one event and any other event or events there is no mutual exclusiveness. Shall I put it that way? This is the doctrine, the highest doctrine of Mahayana Buddhism, which you could call the doctrine of the mutual interpenetration of all things or the mutual interdependence of all things. And it’s symbol is the…what is called Indra’s net that is used in the Avatamsaka Sutra. Imagine at dawn a multidimensional spider’s web covered in dew. A vast vast spider’s web that is the whole cosmos. And is not only a kind of a flat thing, but a solid thing, and has solid in four, five, six and n dimensions covered with jewels of dew, all of which have rainbow coloring. And every drop of dew contains in it the reflection of every other drop of dew. And since every drop of dew contains the reflections of all the others, each reflected drop of dew contains the reflections, you see, of all the others and so ad infinitum.

Now this is the Mahayana vision of the world. Which is to say this is relativity. That whatever exists in this world, and is characterized as something particular, as a thing, as an event, as something or other, you see, as a unit, this does not exist without all other such things and events. So that you might say any one event implies all events, and all events, the total universe, past, present, and future, depends on every single member. In other words, you may say “I can understand that I depend on this whole universe. There could not be me unless there was everything else.” It is harder to see the corollary of that, that the whole universe depends on you. You might say “Well, how can that be? Because I come into being and then I got out of being. And when I’m…before I was born I’m sure the universe was here, and after I die I’m sure it will go on. How can you say then that the whole thing depends on me?” Very simply. It depends on your…supposing you’re dead, and we’re talking about someone in the past. Let’s say we’re talking about Socrates. And I’m going to say this whole universe depends on Socrates. I may put it more exactly. It depends on Socrates having existed.

You see your parents now…some of your parents may be alive but some of parents may be dead. Without your parents you would not have come into being. So you depend on your parents even when your parents have gone. So everything…even when you disappear, the universe will still depend on you. On your having been here. Or if you have not yet arrived, it depends on your going to be here. So we can say…obviously, going back to Socrates…the fact that Socrates existed tells us something about the kind of world we’re living in. This world once Socratized, and that Socrates and his wisdom was a symptom of the kind of universe we’re living in in just the same way as I showed you that an apple is a symptom of a tree, certain kind of tree; tells us something about that tree: what it functions, how it produces things. So a world which produced Socrates or a world which produced John Doe, who was nobody in particular and nobody ever remembered him or though to write his biography, nevertheless, for all his obscurity the whole universe depends on him and it depends equally on every fruit fly, every gnat, every vibration of every gnat’s wing, and it depends on every last electron, however brief its manifestation may be.

So that…what this is saying is that everything that there is implies everything else. And all those other things, collectively, in their totality, in which we the universe in turn imply each individual object, event, and so on. That’s the meaning of Indra’s net. So that, this is called in Zen, to take up a blade of grass and use it as a golden Buddha 16 feet high. When you have a chain and you pick up a link all the other links come up with it, you see, because it implies if this is a link, it is a link in a chain. If it isn’t, it’s just an oval piece of metal. But if it’s a link, up come all other links.

So if you are an event, every event…no…there’s no such thing as a single event. The only possible single event is all events whatsoever. That could be regarded as the only possible atom; the only possible single thing is everything. But the things that we call things all imply each other. We know what we are only in relation to what we aren’t. We know of the sensation of one’s self only in relation to a sensation of something other. So the other goes with the self as the back goes with the front. And your life, however short, everything depends on it. If that did not happen, nothing would happen. So in this sense the whole world bears your signature. It would not be the same world if it weren’t for you.

You’ve heard haven’t you, what is called the pathetic fallacy? This was a idea of the 19th century which said that it was false and wrong to project human feelings on the world. The wind in the pine trees is not sighing. It’s you who are sighing. The Sun is not happy. It’s you who are happy when the Sun shines. So don’t mix up your happiness with the Sun. The Sun has no feelings. The Sun is not human. The wind has no feeling, and is not human.

The poet says

The moon doth with delight
Look round her when the heavens are bare;

And the logician says “No. The poet looks round with delight at the moon in the bare heavens.”

How awful. I mean if that’s what, if that’s the point, you see, better not say any poetry. Just have prose.

But actually the moon does look round with delight when the poet looks round with delight, because the world of which one symptom is the moon is the same world of which another symptom is the poet. They go together. A world where there is a moon implies a world where there is a poet. A world where there is a poet implies a world where there is a moon. So in this sense the moon can be said to look round with delight through the agency of the poet. ‘Cause you can’t separate poet and moon, just as you can’t separate head and feet without destroying the unity of the body.

So in that sense then, this whole world is a human world and we should not take this silly attitude or philosophy called the philosophy of the pathetic fallacy which says outside our skins it’s all inhuman and dumb and blind force, and only inside the skin is there the human world. All this world is human because it depends not only on the existence of humanity in general but on the existence of Mary Smith in particular. So the whole world is covered, as it were, with your personal signature. But at that moment when you suddenly seem to be everything, and to be Mr. A, you know, you suddenly see the obverse of this, that your particular personality is nothing at all without everything else; without everybody else.

I need, in order to be Alan Watts, I need every single other human being and the uncontrollable otherness of all those other human beings that I can’t do anything about. They’re going to be themselves whatever I do. And yet at the same time I, I depend on all their difference from me, and yet it…they all depend likewise on me. So that I’m in a very funny position. The moment I would be ego-less and say I’m nothing without you, then suddenly I find I’m, I’m the kingpin; they all depend on me. Then suddenly then when I get swellheaded about being the kingpin I find I’m nothing at all without them. So everything keeps going bloorp, bloorp, bloorp, bloorp. In other words, no matter how much you think you’ve got it in one state it transforms itself into the other. That’s the Ji-Ji-Mu-Ge.

Now, in Ji-Ji-Mu-Ge you see you got a vision of the world in which everybody is boss and nobody is boss. There is no one boss who governs the whole thing. It takes care of itself. It’s a colossal democracy. But yet every man, and every Uguisu, and every snail is king in this world, and at the same time is commoner. And that’s how it works. And there is no great king. Although in Hinduism they have an idea, a very strange one to us, called Ishvara. Ishvara means the supreme personal god; the top being in the Deva world. And they…many Buddhist believe that there is such a god; there is a ruler of the universe. But, he is lower than a Buddha. Because in the course of the endless cycles Ishvara will dissolve into nothing. All gods, all angels are within the round of being. It’s a very curious idea to our, our minds. And, therefore, although Buddhist believe in god in that sense, they don’t take it importantly. There are no shrines in Buddhism to Ishvara.

So then, it is through Ji-Ji-Mu-Ge, this idea of the mutual interpenetration and interdependence of all things that we have the philosophical basis for Zen as a practical non-intellectual way of life. Because of the realization that the most ordinary event, the charcoal brazier, the mat, soup for dinner, sneezing, washing your hands, going to the bathroom, everything…all these so called events, separate events, imply the universe. So this is why Zen people will use the ordinary event to demonstrate the cosmic and the metaphysical. Only they don’t rationalize it that way.

To see infinity in a grain of sand and eternity in an hour is still Ri-Ji-Mu-Ge and not Ji-Ji-Mu-Ge. Ji-Ji-Mu-Ge is when you offer somebody the grain of sand for god’s sake stop thinking about eternity. Here’s just the grain of sand. There’s no difference between the grain of sand and eternity. SO you don’t have to think about eternity as something implied by the grain of sand. The grain of sand is eternity. So in the same way exactly, our sitting here at this moment is not something different from nirvana. We are nirvana as sitting here exactly like this, you see. So you don’t have to say any philosophical comment on the grain of sand or one our sitting here. That’s called “legs on a snake” or “a beard on a eunuch”. You put legs on a snake you see and you embarrass the snake in its motion and eunuch doesn’t need a beard. We would say, in our idiom, “don’t gild the lily” or Zen would say “don’t put frost on top of snow”.

So all what you might call specifically religious activity is legs on a snake. Eventually this is going to be eliminated just as eventually we hope that government will be eliminated and will become unnecessary because every individual will be self governing and, therefore, relate properly to his brother. And the state will vanish. So, too, at the same time the church will vanish. And that’s why in the, in the book of Revelation, in the New Testament, it is said that in heaven there is no temple because the whole place is the temple. So in…when we achieve the fulfillment of Buddhism there is no Buddha, no temple, no gong, no bell, because the whole world is the sound of the bell and the image of Buddha is everything you can look at.

So a Zen master was asked “Mountains and hills, are they not all forms of the body of Buddha?” The master replied, “Yes, they are, but it’s a pity to say so.”

Further Reading
[1] Zen direct to you http://www.japantimes.co.jp/culture/2007/10/11/arts/zen-direct-to-you/ Retrieved 2017-08-07
[2] Zen Festmények Zen Painting https://terebess.hu/zen/sengai.html Retrieved 2017-08-07
[3] Liang Kai Paintings http://www.chinaonlinemuseum.com/painting-liang-kai.php Retrieved 2017-08-07
[4] Liang-Kaj Csan Festményei https://terebess.hu/zen/liangkaj.html Retrieved 2017-08-07

Reliability, Confidence, and Sample Size, Part II

In Part I the problem was to find the sample size, n, given failure count, c = 0, confidence level = 1 – P(c = 0), and minimum reliability = (1 – p’). The table giving sample size, n, with failures c = 0, for certain common combinations of confidence level and minimum reliability is reproduced below.

While I would like that none of the samples fail testing, failures do happen. Does that mean testing should stop on first fail? Are the test results useless? In this part I will flip the script. I will talk about what value I can extract from test results if I encounter one or more failures in the test sample.

I start with the binomial formula as before

It gives us the likelihood, P(x = c), of finding exactly c failures in n samples for a particular population failure rate p’. (Note that 1 – P(x c) is our confidence level, and 1 – p’ = q’ is our desired reliability.)

However, knowing the likelihood of finding just c failures in n samples isn’t enough. Different samples of size n from the same population will give different counts of failures c. If I am okay with c failures in n samples, then I must be okay with less than c failures, too! Therefore, I need to know the cumulative likelihood of finding c or less failures in n samples, or P(x c). That likelihood is calculated as the sum of the individual probabilities. For example, if c = 2 samples fail, I calculate P(x 2) = P(x = 2) + P(x = 1) + P(x = 0).

For a particular failure rate p’, I can make the statement that my confidence is 1 – P(x c) that the failure rate is no greater than p’ or alternatively my reliability is no less than q’ = (1 – p’).

It is useful to build a plot of P(x c) versus p’ to understand the relationship between the two for a given sample size n and failure count c. This plot is referred to as the operating characteristic (OC) curve for a particular n and c combination.

For example, given n = 45, and c = 2, my calculations would look like:

The table below shows a few values that were calculated:

A plot of P(c 2) versus p’ looks like:

From the plot I can see that the more confidence I require, the higher the failure rate or lesser the reliability estimate will be (e.g. 90% confidence with 0.887 reliability, or 95% confidence with 0.868 reliability.) Viewed differently, the more reliability I require, the less confidence I have in my estimate (e.g. 0.95 reliability with 40% confidence level).

Which combination of confidence and reliability to use depends on the user’s needs. There is no prescription for choosing one over another.

I may have chosen a sample size of n = 45 expecting c = 0 failures for testing with the expectation of having 90% confidence at 0.95 reliability in my results. But just because I got c = 2 failures doesn’t mean the effort is for naught. I could plot the OC curve for the combination of n, and c to understand how my confidence and reliability has been affected. Maybe there is a combination that is acceptable. Of course, I would need to explain why the new confidence, and reliability levels are acceptable if I started with something else.

 

 


Operating characteristic curves can be constructed in MS Excel or Libre Calc with the help of BINOM.DIST(c, n, p’, 1) function.

Once I have values for p’ and P(c ≤ 2), I can create an X-Y graph with X = p’, and Y = P(c 2).

Links
[1] Burr, Irving W. Elementary Statistical Quality Control. New York, NY: Marcel Dekker, Inc. 1979. Print. ISBN 0-8247-6686-5

Reliability, Confidence, and Sample Size, Part I

Say I have designed a widget that is supposed to survive N cycles of stress S applied at frequency f.

I can demonstrate that the widgets will conform to the performance requirement by manufacturing a set of them and testing them. Such testing, though, runs headlong into the question of sample size. How many widgets should I test?

For starters, however many widgets I choose to test, I would want all of them to survive i.e. the number of failures, c, in my sample, n, should be zero. (The reason for this has more to do with the psychology of perception than statistics.)

If I get zero failures (c = 0) in 30 samples (n = 30), does that mean I have perfect quality relative to my requirement? No, because the sample failure rate, p = 0/30 or 0%, is a point estimate for the population failure rate, p’. If I took a different sample of 30 widgets from the same population, I may get one, two, or more failures.

The sample failure rate, p, is the probability of failure for a single widget as calculated from test data. It is a statistic. It estimates the population parameter, p’, which is the theoretical probability of failure for a single widget. The probability of failure for a single widget tells us how likely it is to fail the specified test.

If we know the likelihood of a widget failing the test, p’, then we also know the likelihood of it surviving the test, q’ = (1 – p’). The value, q’, is also known as the reliability of the widget. It is the probability that a widget will perform its intended function under stated conditions for the specified interval.

The likelihood of finding c failures in n samples from a stable process with p’ failure rate is given by the binomial formula.

But here I am interested in just the case where I find zero failures in n samples. What is the likelihood of me finding zero failures in n samples for a production process with p’ failure rate?

If I know the likelihood of finding zero failure in n samples from a production process with p’ failure rate, then I know the likelihood of finding 1 or more failures in n samples from the production process, too. It is P(c ≥ 1) = 1 – P(0). This is the confidence with which I can say that the failure rate of the production process is no worse than p’.

Usually a lower limit is specified for the reliability of the widget. For example, I might want the widget to survive the test at least 95% of the time or q’ = 0.95. This is the same as saying I want the failure rate to be no more than p’ = 0.05.

I would also want to have high confidence in this minimum reliability (or maximum failure rate). For example, I might require 90% confidence that the minimum reliability of the widget is q’ = 0.95.

A 90% confidence that the reliability is at least 95% is the same as saying 9 out of 10 times I will find one or more failures, c, in my sample, n, if the reliability were less than or equal to 95%. This is also the same as saying that 1 out of 10 times I will find zero failures, c, in my sample, n, if the reliability were less than or equal to 95%. This, in turn, is the same as saying P(0) = 10% or 0.1 for p’ = 0.05.

With P(0) and p’ defined, I can calculate the sample size, n, that will satisfy these requirements.

The formula can be used to calculate the sample size for specific values of minimum reliability and confidence level. However, there are standard minimum reliability and confidence level values used in industry. The table below provides the sample sizes with no failures for some standard values of minimum reliability and confidence level.

What should the reliability of the widget be? That depends on how critical its function is.

What confidence level should you choose? That again depends on how sure you need to be about the reliability of the widget.

Note: A basic assumption of this method is that the failure rate, p’, is constant for all the widgets being tested. This is only possible if the production process producing these widgets is in control. If this cannot be demonstrated, then this method will not help you establish the minimum reliability for your widget with any degree of confidence.

Links
[1] Burr, Irving W. Elementary Statistical Quality Control. New York, NY: Marcel Dekker, Inc. 1979. Print. ISBN 0-8247-6686-5

Some Observations and Thoughts on Design Controls

In my role as a quality engineer supporting product design and development at various medical device manufacturers I got practical experience with each company’s design and development process. As a matter of regulation[1], each medical device manufacturer has procedures that control the design of their products. Unfortunately, they are not particularly useful.

I’ve observed that the Quality function at these companies develops and deploys all the procedures that the Quality System regulations require[2]. However, professionals in the Quality function typically don’t have the subject matter expertise in a particular function such as product design and development or manufacturing to develop usable procedures for that function.

Here I share an example product design and development procedure typical of those I have seen deployed:

This type of process, laid out in the order of the text of the regulation, would suggest that product design and development is a sequence of steps executed in series.

At first glance it seems logical and sensible. First you catalog the user needs. Next you convert those user needs into design inputs (i.e. engineering requirements.) You then transform the design inputs through the design process into design outputs (i.e. drawings or prototypes.) Those design outputs are then verified (i.e. inspected and tested) against the design inputs. After that the design is validated by the user in the actual or simulated use environment. And finally, the design is transferred to manufacturing for mass production.

It wrongly suggests, albeit implicitly, that these steps also represent phases of design and development where a review is conducted after each block, and that a single traceability matrix, with columns corresponding to each block, is enough to capture the activity of the total design effort.

I have tried to figure out how this would work for a design involving multiple components that are assembled together, but I cannot find a way. This type of design for the product design and development process is fatally flawed as it doesn’t model the real nature of products which is often components/systems embedded within systems. Trying to map the total design effort into this format is like trying to fit a square peg in a round hole, an impossible and ultimately frustrating exercise.

Just because language is linear, in that ideas are expressed one after the other as the regulation does, doesn’t mean that the process being described is linear, too. In fact, the design and development process is most certainly not linear. It is deeply iterative with iterations built within iterations!

The FDA’s “Design Control Guidance for Medical Device Manufacturers”[3] provides an explanation of the iterative nature of the design and development process. The guidance includes a simplified process flow chart, but it does not adequately communicate the complexity that makes up the actual design and development process. The guidance even explicitly says so.

In practice, feedback paths would be required between each phase of the process and previous phases, representing the iterative nature of product development. However, this detail has been omitted from the figure…

The language of the guidance in the above paragraph unfortunately implies that each block of the waterfall design process is a phase. It clarifies this further on where it says:

When the design input has been reviewed and the design input requirements are determined to be acceptable, an iterative process of translating those requirements into a device design begins. The first step is conversion of the requirements into system or high-level specifications. Thus, these specifications are a design output. Upon verification that the high-level specifications conform to the design input requirements, they become the design input for the next step in the design process, and so on.

This basic technique is used throughout the design process. Each design input is converted into a new design output; each output is verified as conforming to its input; and it then becomes the design input for another step in the design process. In this manner, the design input requirements are translated into a device design conforming to those requirements.

While the regulation does not prescribe a method for designing and developing a product, the guidance does point in a particular direction. The best representation I could find that captures the direction in the guidance is this graphic adapted from “The House of Quality” by John Hauser and Don Clausing[4]:

The first “house” shows the “conversion of the requirements [Customer attributes] into system or high-level specifications [Engineering characteristics]”. The body of the house allows for the verification that “high-level specifications conform to the design input requirements”. The engineering characteristics then “become the design input for the next step in the design process, and so on.

It’s obvious from the linked houses and the guidance that verification is not a one time or single type of activity. It is performed at each step of the design and development process wherever inputs are converted to outputs. Implicit in this point is that the type of verification is unique to the particular step or phase of the design and development process.

Each house may be thought of as a phase of the design and development process. The houses offer natural breaks. The design process of the next phase, converting inputs into outputs, depends on the successful completion of the previous phase, so it is nearly impossible to move too far down the process as gaps will be immediately apparent!

Each house can be considered its own traceability matrix where every design output is tied to one or more design inputs. And because the houses are all linked to one another it is possible to trace an attribute of the manufactured product all the way back to the customer need it helps address.

While they may not have a firm conceptual understanding of the design and development process, and thus cannot explain it, I believe most engineers have an instinctual feel for it in practice. But a poorly designed design and development process creates unnecessary and insoluble problems for project teams. The teams I’ve been on have responded to such hurdles by running two parallel processes: one that is the practical design and development effort, and the other is the documentation effort—a hidden factory. I don’t think it’s possible to calculate the cost of such waste.

Links
[1] 21 CFR Part 820.30 (a) https://www.ecfr.gov/cgi-bin/text-idx?SID=a018454b01dab73d0d1cef9f95be36a9&mc=true&node=pt21.8.820&rgn=div5#se21.8.820_130 Retrieved 2017-07-05
[2] QSR Required Procedures https://shrikale.wordpress.com/2017/05/18/qsr-required-procedures/ Retrieved 2017-07-05
[3] Design Control Guidance For Medical Device Manufacturers https://www.fda.gov/RegulatoryInformation/Guidances/ucm070627.htm Retrieved 2017-07-05
[4] The House of Quality. Harvard Business Review, pages 63-77, Vol 66 No 3, May 1988.
[5] Product Design and Development, 5th Edition. McGraw Hill, 2016.

Whose Measurement is Right?

Every company I’ve worked for inspects the product it receives from its suppliers to determine conformance to requirements. The process is variously referred to as incoming inspection or receiving inspection.

Sometimes the receiving inspection process identifies a lot of product that fails to conform to requirements. That lot is subsequently classified as nonconforming material and quarantined for further review. There are many reasons why a lot of product may be classified as nonconforming. Here I wish to focus just on reasons having to do with measurement.

Once a company discovers nonconforming parts, it usually contacts its supplier to share that information. It is not unusual, however, for the supplier to push back when their data for the lot of product shows it to be conforming. So, how can a given lot of product be both conforming and nonconforming? Who is right?

We need to recognize that measurement is a process. The measured value is an outcome of this process. It depends on the measurement tool used, the skill of the person making the measurement and the steps of the measurement operation. A difference in any of these factors will show up as a difference in the measured value.

It is rare that a measurement process is the same between a customer and its supplier. A customer may use different measurement tools than its supplier. For example, where the customer might have used a caliper or micrometer, the supplier may have used an optical comparator or CMM. Even if both the customer and the supplier use the same measurement tool, the workers using that tool are unlikely to have been trained in its use in the same way. Finally, the steps used to make the measurement, such as fixturing, lighting and handling the part, which often depend on the measurement tool used, will likely be different, too.

Thus, more often than not, a measurement process between a supplier and a customer will be different. Each measured value is correct in its context—the supplier’s measurement is correct in its context, as is the customer’s measurement in its context. But because the measurement process is different between the two contexts, the measured values cannot be compared directly with one another. So it is possible that the same lot of product may be conforming per the supplier’s measurements and nonconforming per the customer’s measurements.

But why are we measuring product twice: once by the supplier and again by the customer? Measurement is a costly non-value adding operation, and doing it twice is excess processing–wasteful. One reason I’ve been told is this is done to confirm the data provided by the supplier. But confirmation is possible only if the measurement process used by the customer matches the one used by the supplier.

Besides, if we are worried about the quality of supplier data, we should then focus efforts on deeply understanding their measurement process, monitoring its stability and capability, and working with the supplier to improve it if necessary. With that we should trust the measurement data the supplier provides and base our decisions on it, and eliminate the duplicate measurement step during receiving inspection.

Links
[1] Eliminate Waste in Incoming Inspection: 10 ideas of where to look for waste in your process http://www.qualitymag.com/articles/92832-eliminate-waste-in-incoming-inspection Retrieved 2017-06-29

Above All, Don’t Wobble

In walking, just walk. In sitting, just sit. Above all, don’t wobble.
– Yúnmén

The companies I’ve worked for have been neurotic. They dither. When decisions are made they have an irrational and anxious quality about them.

My experience of work can be described as a shuddering paralysis. In an effort to take everything into account teams I’ve been on enter into an infinite regression of analysis that often takes us off course, delaying action. (I have been guilty of contributing to this.) However, the essence of a business is to act, to do.

When we do act, we don’t just act, but worry about whether that action is the best possible; we complain about all the flaws we find in the method; we even wonder whether the goal is the right goal. So our attention is split, bouncing between acting and thinking. Instead of moving gracefully toward our goal, we wobble. I wobble.

Perhaps Yúnmén wouldn’t mind if I rephrased his quote as “In planning, just plan. In doing, just do. Above all, don’t wobble.”

Retraining Can’t Fix This

In the course of an average workday we make hundreds of decisions. Some of those decisions require engaging our conscious awareness. In my previous post I described how the quality of those decisions deteriorate as that awareness or willpower fatigues with use.

However, there are decisions where human error occurs with certainty even if our attention is totally focused on the task. Consider the Muller-Lyer[1] illusion below:

The two vertical lines are of the same length. Even after knowing this, we all continue to perceive the line on the left to be longer than the line on the right. The “fact” that the two lines are of different lengths is simply obvious to us. Because of its obviousness we don’t stop to check our judgment before acting on it. Such actions, based on erroneous perception, are likely to produce faulty outcomes.

This error in our human perception/cognition system is hard-wired into our brains. No amount of retraining or conscious effort will correct it. So corrective actions that identify retraining as the way to prevent recurrence of this type of error won’t be effective. It will only serve to demoralize the worker. What, then, is an effective corrective action for such errors?

We can develop and use tools and methods that circumvent the brain’s perception/cognition system, for example with an overlay (red lines in the figure below), or actually measuring each line and comparing those values to one another. This does add a step to the evaluation process; an after-the-fact fix to a faulty design. Ideally, though, we would want our designs to take into account human limitations and avoid creating such illusions in the first place.

Links
[1] Muller-Lyer illusion https://en.wikipedia.org/wiki/Muller-Lyer_illusion Retrieved 2017-06-22

Human Error

Often, investigators identify the root cause of a problem as human error. But what exactly is human error?

An action may be judged as an error only in relation to a reference or standard. So first a standard on how to perform the task must exist. Sometimes such a standard is defined in a documented procedure. On occasion it may also be taught by a master to an apprentice on the job. Most times we just figure it out through a combination of past experience, current observations, and some fiddling. Human error, then, is action by a human that deviates from the standard.

When we judge the root cause of a problem as human error we’re making certain assumptions: 1] that a standard exists, and 2] the standard, if it exists, is adequate to the degree that mindfully following it produces the expected outcome.

Let’s grant that both the above assumptions are true, and even grant that the root cause of a problem was the failure of the worker to follow the standard. What, then, should the corrective action be that will prevent the recurrence of the problem? In my experience it has almost always been defined as “retraining”. But such a corrective action assumes that the worker failed to follow the standard because they don’t know it. Is this true? If not, retraining is pure waste and won’t do a damn thing to prevent the recurrence of the problem.

If a proper standard exists and the worker has been trained to it, then there must be some other reason for their failure to follow it. Skill-based errors (i.e. slips and lapses) can occur when the worker is unable to pay attention to or focus on performing the task they are otherwise familiar with. So it’s not a training issue. In my previous post I wrote about how willpower, our conscious awareness, is like a muscle. It can fatigue from use. As willpower is depleted the mind resorts to mental shortcuts or habits. This is how errors creep in.

We should not rely only on our ability to remain attentive and focused to ensure that the task is performed without failure. For that we must design tasks in such a way that failure is unlikely, if not impossible, to occur. Through design thinking we can develop tools, methods, and systems that help us perform better.

Links
[1] Understanding human failure. http://www.hse.gov.uk/construction/lwit/assets/downloads/human-failure.pdf Retrieved 2017-06-15