Tere are four main reasons why I wrote this book. First, six sigma consultants
have taught us that people do not need to be statistical experts to gain benefts from applying methods under such headings as “statistical quality control”
(SQC) and “design of experiments” (DOE). Some college-level books intertwine the methods and the theory, potentially giving the mistaken impression
that all the theory has to be understood to use the methods. As far as possible,
I have attempted to separate the information necessary for competent application from the theory needed to understand and evaluate the methods.
Second, many books teach methods without sufciently clarifying the context
in which the method could help to solve a real-world problem. Six sigma, statistics and operations-research experts have little trouble making the connections
with practice. However, many other people do have this difculty. Terefore, I
wanted to clarify better the roles of the methods in solving problems. To this
end, I have re-organized the presentation of the techniques and included several complete case studies conducted by myself and former students.