ABSTRACT
Shewhart studied variation during his work at Bell Telephone Laboratories in the 1920s. His studies included variation observed in nature, as well as that found in manufacturing environments. He observed that in nature, and in certain controlled experiments, he could predict the limits of variation in samples taken from a given population. However, in manufacturing he noted that the samples he studied rarely followed a predictable pattern. Many were wildly erratic and unpredictable. In the pharmaceutical industry, this erratic behavior leads to failed batches, repeated tests, raised costs, damaged quality, and deviations.
