Mistake proofing or poka-yoke
Made famous by the Japanese auto makers, poka-yoke is simple but powerful in reducing variation, deviations, and discrepancies. The goal is to make activities as mistake-proof
as possible by physical means or by procedures that are difficult to do incorrectly. The classical physical example is to
put a mechanical stop on a drill press to prevent the drillbit from making a hole that is too deep. In a paperwork process,
colored pages are used to clearly identify certain documents.
Control what can be controlled
Although controlling what can be controlled may appear to be an obvious idea, many factors are commonly ignored during normal
operations. Perceived to be noncritical process parameters, they are left to float within some specified range. However, variables
should be controlled to the fullest extent with the highest accuracy possible without incurring great expense or requiring
great effort. Again, controlling only one factor will have a trivial impact, but a culture of controlling hundreds will reduce
common cause variation. The tools discussed in this article require support from management, but it is that support that makes
implementation so powerful.
Lynn D. Torbeck is a statistician at PharmStat Consulting, 2000 Dempster, Evanston, IL 60202, tel. 847.424.1314, LDTorbeck@PharmStat.com
1. D.C. Montgomery and G. C. Runger, Applied Statistics and Probability for Engineers (Wiley, New York, NY, 1994), p. 834.
2. P. R. Scholtes, The Team Handbook (Joiner Associates, Madison WI, 1988), p. 2–28.