Dorian Shainin's Influence on Quality Professionals Part IV
Multi-vari and pre-control charts in our final Shainin column.
Multi-vari charts are a useful tool for presenting analysis of variance data in graphical form. They can identify patterns of variation, on a single chart, from many causes.
In a multi-vari study, samples are taken systematically from the process in order to capture the effect that various times and location have on variation. It can be an excellent tool to use early in the progressive search for a dominant cause (the Red X).