Is the Six Sigma statistical model technically sound?
Overview Purists challenge the statistical component of the Six Sigma model on the grounds that it is, at worst, fundamentally flawed and, at best, based on very tenuous grounds. There are a number of reasons for this. The critique and response to the critique given in this chapter are prompted by four constructive and positive considerations:
to place potential users in a better position to deal with technical queries on the standard Six Sigma statistical model as they arise;
to point out frailties in the conventional or original Six Sigma statistical model and to propose more appropriate metrics where required by a particular situation;
to indicate the probable marketing reasons for the model that has given the initiative its name; and
to put this matter of model frailty into proper perspective in relation to the merits of the overall Six Sigma business initiative.