As an Engineer, I am very interested in Cause and Effect phenomenon. We have always been trained to understand that correlation does not mean causality. But then how does one establish causality? The most common method is to use randomized blind studies.

In this post I want to highlight two pioneers who have established paradigms for understanding cause and effect. They are David Fume and Sir Bradford Hill. Understanding their approaches provides a deeper philosophical understanding on cause and effect.

David Hume:

David Hume (1711 – 1776) was a great Scottish Philosopher who authored “A treatise of human nature.” In this, he gives eight rules to clearly determine cause and effect. I have paraphrased some of them for clarity.

1. The cause and effect must be contiguous in space and time.
2. The cause must be prior to the effect.
3. There must be a constant union between the cause and effect. It is chiefly this quality that constitutes the relation.
4. The same cause always produces the same effect, and the same effect arises from the same cause.
5. To add to rule 4, where several different objects produce the same effect, it must be by means of some quality, which we discover to be common amongst them.
6. The difference in the effects of two resembling objects must proceed from that particular, in which they differ. For as like causes always produce like effects, when in any instance we find our expectation to be disappointed, we must conclude that this irregularity proceeds from some difference in the causes.
7. When any object increases or diminishes with the increase or diminution of its cause, it is to be regarded as a compounded effect, derived from the union of several different effects, which arise from the several different parts of the cause. The absence or presence of one part of the cause is supposed to always be matched with the absence or presence of a proportional part of the effect. This constant conjunction sufficiently proves that the one part is the cause of the other.
8. An object, which exists for any time in its full perfection without any effect, is not the sole cause of that effect, but requires to be assisted by some other principle, which may forward its influence and operation. For as like effects necessarily follow from like causes, and in a contiguous time and place, their separation for a moment shows, that these causes are not complete ones.

The particular section of Hume’s treatise is available here. https://ebooks.adelaide.edu.au/h/hume/david/h92t/B1.3.15.html

Sir Bradford Hill:

Sir Bradford Hill (1897–1991) is most famous for the Hill criteria in epidemiology. The hill criteria, described first in his paper “The Environment and Disease: Association or Causation”, again provides a list of rules to determine causality. As a side note, his paper used smoking-cancer link as an example, and this was refuted strongly by Sir Ronald Fischer. That will be a post for another day.

The Hill criteria consist of 9 rules, and there are some overlaps with Hume’s rules. Hill has given the following background for his criteria.

“None of these nine viewpoints can bring indisputable evidence for or against a cause and effect hypothesis …. What they can do, with greater or less strength, is to help answer the fundamental question—is there any other way of explaining the set of facts before us, is there any other answer equally, or more, likely than cause and effect?”

1. Strength: A strong correlation is a pre-requisite to consider causality.
2. Consistency: To quote Hill “Has it been repeatedly observed by different persons, in different places, circumstances and times?” This answers the reproducibility question. Is the effect reproducible under different set of criteria?
3. Specificity: Ideally, in epidemiology, an effect is linked with one specific cause. In Hill’s eyes, the more specific the association to a specific cause, the stronger the argument is in favor of causation. In his words, “If the association is limited to specific workers and to particular sites and types of disease and there is no association between the work and other modes of dying, then clearly that is a strong argument in favor of causation.”
4. Temporality: Hill presented this criterion as a question – which is the cart (effect) and which is the horse (cause)? As noted before, the cause must always come before the effect, on a timeline.
5. Biological gradient: The keyword here is “gradient”. Is there a comparable increase in effect, with an increase in the cause factor? In his paper, Hill gave the example of death rate to number of cigarettes smoked in a day. This is a kind of feedback loop.
6. Plausibility: This is my favorite criterion in the list. Is the cause and effect theory likely to happen from a logic stand point? I was very excited when I saw that Hill actually quoted Sherlock Holmes in his paper. “In short, the association we observe may be one new to science or medicine and we must not dismiss it too light-heartedly as just too odd. As Sherlock Holmes advised Dr Watson, ‘when you have eliminated the impossible, whatever remains, however improbable, must be the truth.’”
7. Coherence: To expand upon criterion 6, Hill wanted to make sure that the cause and effect theory did not go against existing theories. There is always more buy-in when the theory does not conflict with existing knowledge.
8. Experiment: One must always provide experimental evidence to back up the cause and effect theory.
9. Analogy: If there is supporting evidence on similar factors, it makes it easier to establish causality.

Bradford Hill’s seminal paper is available here. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1898525/pdf/procrsmed00196-0010.pdf

Final words:

One must learn from great thinkers from other fields. In your next problem solving project, when you are trying to perform root cause analysis, will you be able to use Hume’s rules or Hill’s criteria?

Always keep on learning…

I have an ongoing interest in Medical Device packaging. When I started at my current job a while back, my manager told me that the packaging operation is most critical operation for a sterile Medical Device. The product quality does not matter if the device is not provided sterile for the end user. The qualifications of new packaging configuration and the packaging process soon became my areas of interest.

The concept of “worst-case” is rooted in product reliability and good product design practices. The applicable industry standards for packaging Medical Devices are ISO 11607 parts 1 and 2. ISO 11607 part 1 has the following section detailing the use of “worst-case” product configuration for qualifying a packaging system.

“When similar medical devices use the same packaging system, a rationale for establishing similarities and identifying the worst-case configuration shall be documented. As a minimum, the worst-case configuration shall be used to determine compliance with this part of ISO 11607.”

For a Medical device design engineer or a packaging engineer, this determination of the worst-case comes natural. It is based on engineering judgment and intuition. However, one might find it easier if this can be documented objectively. The following matrix might be useful to document the worst-case configuration. Perhaps one can utilize a scoring system (1 through 5, where 1 -> Best case, and 5 -> Worst case) for each of the items detailed in the table below. Thus, the product with the highest score can be determined to be the worst-case configuration.

Please note the worst-case for qualification tests may not always represent real life scenarios. However, qualifying using the worst-case provides assurance that the product can meet real life scenarios.

The scoring sheet sample can be downloaded here (worst-case score sheet).

Disclaimer: Please note that this post is purely based on my opinion and not to be used as advice. I shall not be responsible for any possible outcomes. Please use at your own discretion.

There is a balance that exists in root cause analysis that is Yin and Yang. In Chinese philosophy, Yin and Yang represents the harmonious balance between seemingly contradictory forces. Light is Yang, darkness is Yin. Hot is Yang, cold is Yin. Top of a hill is Yang, valley of the hill is Yin. The typical representation of Yin and Yang has the white section as Yang and the black section as Yin.

The root cause analysis process can be represented by the simple schematic below:

Once the problem statement is made, one should use divergent thinking to gather more data/information and identify the potential sources of a problem. This should be followed by convergent thinking where one focuses on the true root cause(s). One might use Fishbone diagram as the form of divergent thinking, and five why as the convergent thinking.

Divergent thinking is expansive in nature and lacks focus, thus it is Yin. Convergent thinking, on the other hand is zooming in and direct in nature, thus it is Yang. As with anything else in nature, a good root cause analysis process should have at least one cycle of divergent thinking and convergent thinking. The approach of Yin and Yang creates a complete/whole root cause analysis.

Jumping to conclusions is just Yang. The absence of Yin makes this an imbalanced and wrong approach. As noted above, one may use multiple cycles of divergent thinking followed by convergent thinking. Think of this as a rinse process, purifying your thinking process with each cycle. This will provide clarity in your investigation, and prevent biases that water down your efforts to fix the problem.

As you may have noted, each half (Yin or Yang) also has a dot corresponding to the opposite color. This indicates that within each section, nothing is complete. In my humble opinion, this is similar to the Japanese thinking of wabi-sabi. That is, even within the Yin, it is not completely Yin. There is a dot of Yang in it. Even when we are doing divergent thinking, we are going in a certain direction. Even when we are doing convergent thinking, we are still remaining open.

Always keep on learning…

Having been immersed in TPS (Toyota Production System) or lean, I have been very interested in seeing how many lean practitioners talk about 5S and the importance of a clean and organized desk. It is almost as if, the clean and organized desk indicates a clean and organized mind – making you a more productive worker. As with everything else, generalization is not always a good thing.

The goal of 5S (or Go-Esu as our Japanese counterparts say) is not to clean and have a tidy work place. The goal of 5S is to ensure that any waste becomes immediately visible. I have delved philosophically about how this applies to an office environment, where the work does not always have routine, efficient and predictable attributes.

My own personal experience has been that having a less than tidy desk never hindered my productivity. Sometimes, the opposite was true. My desk may have piles, but the most important projects/documents are always on the top and close to me. Proximity and the order indicate the importance and timeliness requirement of the project.

My goal has been to have an organized mind first, and then an organized desk. It looks like there has been some research done about the cluttered desks, and this is not truly new news. The goal of this post is not to promote cluttered desks. The goal of this post is to promote organized minds through mindfulness.

Einstein is supposed to have asked, “If a cluttered desk is a sign of a cluttered mind, of what, then, is an empty desk a sign?” The cued answer is a tongue-in-cheek “Empty mind.”

A study conducted in 2013 by Kathleen D. Vohs, a behavioral scientist at the University of Minnesota, indicated that a cluttered desk might actually lead to outside the box thinking by allowing one to veer from the conventionally treaded paths. http://pss.sagepub.com/content/24/9/1860

It is true that many great minds have been found to have messy desks.

ALBERT EINSTEIN

STEVE JOBS

MARK TWAIN

But as I stated earlier, the goal of this post is not to promote a cluttered desk. 🙂

I have been trying to have a better organized mind through mindfulness practice. The goal of mindfulness practice is to be aware and to be present at the given moment. Surprisingly this has huge benefits in the hustled world that we live in. Check out this link. http://greatergood.berkeley.edu/article/item/three_benefits_to_mindfulness_at_work

Mindfulness helps in improving our emotional intelligence, and helps us being focused on the task at hand. It provides clarity to our minds.

So let us try to organize our minds, getting rid of clutter leading to clarity and focus. And then, have an organized desk. Maybe, a cluttered desk is not that bad after all.

Keep on learning…

I heard this story when I was a little kid. Now that I am older, I am not able to trace its source. I think it may have been a Zen story. Anyways, the way I remember it is as follows:

There was a famous teacher in a village. Two brothers came to be trained under him. Years went by, and the older brother was getting restless. In his mind, the teacher was partial to his younger brother, and he could not understand why. He is older and felt wiser than the younger brother. But the teacher never gave him any responsibilities.

One day, the older brother went to his teacher and asked him,

“Teacher, why is it that you do not give me any responsibilities? You always seem to be biased towards my younger brother. We came here at the same time, and learned everything together. Yet, you treat him better than you treat me. Why?”

The teacher smiled. He sipped his tea, and then said,

“Let’s do this; why don’t you run to the village center and go to the rice store. Ask the vendor, what is the price of rice? Come back when you are ready.”

The older brother thought this was an easy job. He ran to the village center and asked the vendor the price for rice, and ran back to his teacher.

“It is 10 rupees per kilo.” He said trying to catch his breath.

The teacher asked him. “Is this the price for brown rice?”

“Yes”. The older brother replied.

“What about the white rice?” The teacher asked.

“I do not know.” The older brother replied.

So he ran back again, and asked the vendor for the price of white rice, and ran back to his teacher.

“It is 12 rupees per kilo.” He replied again trying to catch his breath.

“Is there a price discount, if I buy 10 kilos?” The teacher asked.

“I do not know” was the answer again.

The student ran to the village center yet again to gather more information.

“The price is 8 rupees if we buy 10 kilos.” The student responded.

“What about the white rice?” was the next question from his teacher.

Now the student was too tired to run back again, so he sat down ashamed.

The teacher asked for the younger brother to come. He was unaware of any of the happenings.

“Why don’t you run to the village center and go to the rice store. Ask the vendor, what is the price of rice? Come back when you are ready.” The teacher asked the same thing to the younger brother.

“Sure thing, Teacher”, the younger brother replied.

He ran off and came back after a short while.

“The price of rice is 10 rupees per kilo for brown, and 12 rupees per kilo for white. If you buy 10 kilos, you will get a discount of 2 rupees for both brown and white. The new stock is coming in two days, so we might want to wait to get the fresh supply. The vendor also gave his regards to you.” The younger brother replied.

“Thank you, my son. You may go now”, the teacher said.

The teacher took another sip of his tea, and looked at the older brother, and said.

“When you are given a task, always try to see what the big picture is. Try to understand how your seemingly little task aligns with the big task at hand.”

“Do not be a small person caring about only small things and your own small world. Be a big person caring about both small and big things.” The teacher continued finishing his tea.

THE END.

Soon after joining the work force, I came to the realization that I have to move in and out of the big and small picture perspectives. A task or a project sometimes seems to live on even after you are done with it, and it is generally intertwined with multiple other projects. Thus I learned to keep my mind at the task at hand, while keeping my eyes on the big picture.

To me, the younger brother also ensured to maintain a personal interaction with the rice vendor. This is also an important thing to keep in mind.

Always keep on learning, and be ready when you are next asked what the price of rice is.