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Donald J. Wheeler
Many people have been taught that capability indexes only apply to “normally distributed data.” This article will consider the various components of this idea to shed some light on what has, all too...
    Walter Shewhart made a distinction between common causes and assignable causes based on the effects they have upon the process outcomes. While Shewhart’s distinction predated the arrival of chaos theory by 40 years, chaos theory provides a way to understand what Shewhart was talking about....
    Quality-related data collection is useful, but statistics can also deliver misleading and even dysfunctional results when incomplete. This is often the case when information is collected only from surviving people or products, extremely satisfied or dissatisfied customers, or propagators of bad...
    Many different approaches to process improvement are on offer today. An appreciation of the way each approach works is crucial to selecting one that will be effective. Here we look at the problem of production and consider how the different improvement approaches deal with this problem. The...
    man with sunburned shoulders
    As I started reading The Book of Why: The New Science of Cause and Effect, by Judea Pearl and Dana Mackenzie (Basic Books, 2018), I was reminded how often analysts trot out the bromide “correlation is not causation.” It’s a well-known warning. Indeed, I often encourage those learning data...

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