A simulation study was undertaken to quantify the relationship between guard banding, percent tolerance (also known as the precision-to-tolerance [P/T] ratio), and the probability of misclassification – all in the presence of varying distributions for both part values and gage error. A response surface designed experiment was utilized to generate a balanced set of factor level combinations. The following four factors were used to summarize the important characteristics of the gage and part distributions:
1. True value capability index, Ppk. This factor describes variance of the true value population with respect to specification limits, including the centering of the true value mean, , within the specification limits.