A Practical Approach to Quality Control
Rowland H Caplen
Caplen lurks on every quality professional’s bookshelf. At first glance, it’s difficult to see why. The book is unassuming, small, slightly too thick for its size. The cover is white and shows up every sign of oil, lubricant, ink or strawberry jam it comes into contact with. Although it’s been reprinted fourteen times since, the fifth edition dates from 1988 and, despite the author’s doing his best to insert the politically correct him or her alternatives, his feeling seems to be that men do quality and girls (not even women) use typewriters. Yes, in 1988, or whatever edition this passage on the necessity for satisfactory equipment dates from, Caplen writes that “every typist in the company does not need the most expensive, brand new electric typewriter a typewriter of quite modest quality may be adequate for the job”. And Caplen spends more space on quality circles – ten pages – than perhaps they merit. Seriously though, Caplen is a child of his time, who believes that the responsibility for quality resides more with the inspector than the operator. “The operator should be encouraged to regard the inspector as a friend” he writes, adding “who [the inspector] assists him in the tasks of keeping defective work to a minimum”. It’s a selling point on the cover that the entire syllabus of the City and Guilds 743 is included: I’m not sure if the reader will find this as useful, since C∓G 743 has been superseded, even its successor has been superseded.
Against all that, though, is Caplen’s kind, but firm and logical approach to quality control. He takes the reader by the hand and liberally scatters empowerment phrases by which “we” specify any two points on “our” graph or “we” plot an activity frequency distribution curve. There’s examples and diagrams at every step of the way and most chapters end with a few sample exam questions (but not, alas, model answers, apart from brief numeric data) with an estimation of the maximum number of marks which could be achieved.
Caplen doesn’t say anything original in his chapter on frequency distribution curves, but he takes it so slowly and gradually that the standard deviation calculations come, almost, as a pleasant surprise. Control charts are dealt with in some detail, always with practical down to earth examples and then the book gently starts settling down to the design and implementation of quality systems. There’s a brief, but useful, chapter of design of control charts. The information is hard copy paper-based, but not redundant for those who prefer electronic control charts (isn’t that everyone?) And, finally, there’s a brief canter round design of experiments.
When I started studying quality, my team leader produced her battered copy of Caplen for me. I didn’t appreciate it (or even read it) and kept it wrapped up in my desk drawer until I could return it with thanks after a decent interval. As soon as statistics entered the picture, so did Caplen. The book was sitting patiently in the bookshop, obviously aware that there were so many other flashier books available. But after I flicked through it, Caplen ended up in my own bookshelf and it’s been a faithful reference book since. Yes, I understand Caplen’s limitations – there’s no mention of lean manufacturing or six sigma or even (which rather surprised me) continuous improvement. But for good, plain, basic quality assurance, you’ve got to look very hard to find a better introductory text than Caplen.
© Fell Services Ltd., 2004