In Web Browser Stats: Problems With Data Gaps I looked at my website statistics to evaluate how relative usage of Internet Explorer, Firefox, and Google Chrome has evolved over the past year and a half. For part of my analysis, I plotted SPC-type control charts of browser stats using a simple mean ± 3 SD [...]

Last year I wrote an Introduction to Control Charts (Run Charts). I referenced a favorite book of mine, Understanding Variation: The Key to Managing Chaos, by Donald Wheeler of SPC Press, an expert in Statistical Process Control. This book is a quick read, and it’s a great introduction to control charts, written clearly using layman’s [...]

A simple chart can be very useful to check for patterns or errors in your data. Such features of the data may be difficult or impossible to find in the tabulated data, but they jump out from a simple chart.
Jorge Camoes suggests in Validate Your Tables – US Census Bureau Example that we make a [...]

Introduction to Control Charts
While employed as a scientist/engineer for a large manufacturing corporation, I pulled a stint as trainer for my company’s Total Quality program. This role occupied half of my time for three or four years. A large component of our Total Quality initiative was related to Statistical Process Control (SPC). And of all [...]

Statistical Process Control (SPC) is a set of statistical and related methods for monitoring processes with an aim to improve productivity and reduce costs, time, and waste incurred by these processes. In fact, SPC is a philosophy surrounding the monitoring, analysis, and adjustment of process variables to produce continuous improvements in the process.
There are a [...]