A review of “Understanding Variation The Key to Managing Chaos” by Donald J. Wheeler

This book is both insightful and useful. It was recommended to me by members of the Deming Profound Book Club. Wheeler describes how to create control charts and analyse processes using control charts. This book can help you start to use control charts to analyse data from your test and development processes.

Walter Shewhart invented control charts when he was working for Bell Telephones. For the last one hundred years managers and teams have been using control charts. They are used in many industries, but only sometimes used in software development. Testers can use control charts to provide a useful way to analyse the results of performance tests. 

The use of goals and targets to analyse data is contrasted with the use of control charts. Goals and targets are described as “the Voice of the Customer” because it defines what you want. Control charts are described as the “Voice of the Process” because they define what you will get from a system. [1]

Control charts contain time series data, a central line as a visual reference, and upper and lower control limits. Wheeler describes how to calculate the control limits from the variation in the time series data. 

All variation is characterised by control charts as either predictable (within the control limits and so in statistical control) or unpredictable (outside the control limits and so out of statistical control). [3]

A major advantage of “the Control Chart Approach filters out noise by the construction of the control limits. Signals are indicated by points which fall outside the control limits or by obvious non-random patterns of variation around the central line” [4]

Wheeler uses control charts to tell stories about the economy and companies. Each story throws light on a different aspect of the valuable insights provided by using control charts. These stories include sections about how to analyse events that occur rarely and how a company’s performance is affected by an improvement plan.

I used this book to help me create control charts using Geckoboard Datasets AP, the product that I am testing. I have learned so much about the product I test and about how to use control charts by creating control charts. I would encourage you to use this book to start experimenting by creating control charts and so gain insights from your process.

I would also like to thank Rob Park for his help when I had questions about creating and analysing control charts.

References

[1] Understanding Variation The Key to Managing Chaos by Donald J. Wheeler (1993, p79)

[2] Understanding Variation The Key to Managing Chaos by Donald J. Wheeler (1993, p23)

[3] Understanding Variation The Key to Managing Chaos by Donald J. Wheeler (1993, p112)

[4] Understanding Variation The Key to Managing Chaos by Donald J. Wheeler (1993, p30)