By: Davis Balestracci
09/03/2019
As statistical methods become more embedded in everyday organizational quality improvement efforts, I find that a key concept is often woefully misunderstood, if it is even taught at all. W. Edwards Deming distinguished between two types of statistical study, which he called “enumerative” and “analytic.”
The key need in quality improvement is that statistics should relate to reality, which then lays the foundation for a theory of using statistics (analytic). Whether you realize it or not, the perspective from which virtually all college courses and many belt courses are taught is population-based (enumerative), its purpose is estimation.
In a real-world environment, this becomes questionable at best because everyday processes are usually not static populations. Deming was emphatic that the purpose of statistics in improvement is prediction; the question becomes, “What other knowledge beyond probability theory is needed to form a basis for action in the real world?”
Think of population-based statistics as studying a static pond, and a designed study going even further to create a custom-made pond like a swimming pool—a sanitized version of a pond, much easier to study and sample because of reduction of “nuisance” (i.e., everyday) variation.