TABLE OF CONTENTS 'When I use a word', Humpty Dumpty said, in a rather scornful tone 'it means just what I choose it to mean neither more nor less'. 'The question is', said Alice, 'whether you can make words mean so many different things'. 'The question is', said Humpty Dumpty, 'which is to be master that's all'
Through the looking glass, Lewis Carroll
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.
There are five very controversial aspects of the Six Sigma statistical model that are criticized, cause confusion, and hence prompt discussion and resolution:
the different use of the universally accepted term denoting standard deviation, the Greek term ' sigma';
the method of the linking...
