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Many different approaches to process improvement are on offer today. An appreciation of the way each approach works is crucial to selecting an approach that will be effective. Here we look at the problem of production and consider how the different improvement approaches deal with this problem.
EDITORS: Treat Group One, Two, Three, Four as proper nouns. They are referred to in figures and also Wheeler is trying to avoid confusing people re: "groups" in general, vs. "Groups" referred to in figs.
The problem of production
For the purposes of the following discussion a cause-and-effect relationship will exist when changes in the value of a cause result in changes in the value of a product characteristic. Here we will define the effect of a cause to be the variance created in the product stream as the cause varies through its natural range of values. Of course, when the cause is constrained so that it cannot vary, then it will no longer create any variation in the stream of product values.
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Comments
Different Approaches and the High-Reliability Organization
This article is another in a long line of excellent articles on SPC and process improvement. Thanks for this, Don!
I just wanted to add two cents to this, because I have recently had what looked like a good opportunity: to help a healthcare organization in its journey to becoming a High Reliability Organization. The concept came from studies in the late '80s around Aircraft Carrier Group operations and Airline flight operations. The idea is to work a highly complex set of operations and develop processes and systems that yield very high reliability, i.e., very low defective counts.
What evolved from the research were five basic traits or values shared by HROs:
1. Sensitivity to operations - leaders and staff are constantly aware of how processes and systems affect the organization.
2. Reluctance to accept "simple" explanations - HROs recongnize the risk of "common sense" assumpions and failure to dig deeply enough to find the real sources of problems.
3. A preoccupation with failure - every employee at every level is encouraged to identify and (if possible) find solutions to problems.
4. High reliability organizations defer to expertise - leaders at HROs listen to people who have the most knowledge about a task.
5. HROs are resilient - (sometimes "relentless"). This is essentially what Deming called "Constancy of Purpose," but it is also about seeing mistakes as opportunities for improvement, and relentlessly pursuing those opportunities.
The reason I bring this up is that it struck me as we were beginning what looked like a promising journey, it struck me that one of their problems was the problem of rarity. They are looking for problems that occur rarely (the crash of an aircraft, cross-infection in a surgical suite). These fit well into Don's category 4.
The prime contractor I was working for ended up losing the contract before we got very far, but their approach didn't strike me as effective. They immediately decided that the only way for them to make progress was to ignore value 2, because all the healthcare professionals involved thought that complex problem solving paradigms (that included SPC or any other statistical methods) would be too confusing, so they decided to mandate the lean 9-block A3 as their only problem-solving method.
Rare
What is rare is a person like you that could have helped improve their processes. What a shame they chose A3 as a solution. Being generous A3 does address Dr. Shewhart's first step, Specification (What are we trying to accomplish per Don). A3 ignores step two (By what method per Deming) and ignores step 3 judgment (Test of hypothesis per Shewhart). The organization has doomed itself to cycle between intense panic (a rare event occured) and benign neglect (no bad event lately) to use Don's terms, by turning their backs on you and statistical methods.
Great post per usual by Dr. Wheeler and thank you for the thought provoking reply!
Multi Vari
Sometimes a multi vari study is a good compromise between purely experimental and purely observational.
How to measure variation on y axis
Wonderful article Don, thank you.
They axis states "Variation in Product due to Each Cause", how do we calculate these values using a control chart
Regards
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