Statistics for Process Control Engineers

Preface

There are those that have a very cynical view of statistics. One only has to search the Internet to find quotations such as those from the author Mark Twain:

There are three kinds of lies: lies, damned lies, and statistics.Facts are stubborn, but statistics are more pliable.

From the American humourist Evan Esar:

Statistics is the science of producing unreliable facts from reliable figures.

From the UK’s shortest‐serving prime minister George Canning:

I can prove anything by statistics except the truth.

And my personal favourite, attributed to many – all quoting different percentages!

76.3% of statistics are made up.

However, in the hands of a skilled process control engineer, statistics are an invaluable tool. Despite advanced control technology being well established in the process industry, the majority of site managers still do not fully appreciate its potential to improve process profitability. An important part of the engineer’s job is to present strong evidence that such improvements are achievable or have been achieved. Perhaps one of the most insightful quotations is that from the physicist Ernest Rutherford.

If your experiment needs statistics, you ought to have done a better experiment.

Paraphrasing for the process control engineer:

If you need statistics to demonstrate that you have improved control of the process, you ought to have installed a better control scheme.

Statistics is certainly not an exact science. Like all the mathematical ...