Donald J. Wheeler, PhD is a world-renown expert in continuous improvement, having worked with W. Edwards Deming and later writing the classic book Understanding Variation.
Wheeler once wrote and said, "Statistical Process Control is, at its heart, about getting the most from your processes. It is about the continual improvement of processes and outcomes. And it is, first and foremost, a way of thinking... with some tools attached."
I’d like to thank him for providing the perfect quote for a blog about process control charts because measurement, control, and improvement are exactly what they are designed to enable.
What is a Process Control Chart?
Process control charts (or what Wheeler calls "process behavior charts") are graphs or charts that plot out process data or management data (outputs) in a time-ordered sequence. It's a specialized run chart. They typically include a center line, a 3-sigma upper control limit, and a 3-sigma lower control limit. There might be 1- or 2-sigma limits drawn in, as well. The center line represents the process mean or average (and sometimes the median).