The use of capability indices such as Cp, Cpk, and “Sigma” values is widespread
in industry. It is important to emphasize that there are certain crucial assumptions,
which allow the use of such values to have a meaningful interpretation, which are
frequently overlooked. It is the aim of the author to address such issues by the use
of discussion and case studies, and to provide some useful guidelines and insights
when performing capability analysis using Minitab®. Procedures when dealing with
non-Normal data will be considered in the following edition of EXTRAOrdinary
Sense.