Intervals & Tests
This distribution is often used when the measurement system produces only positive measurements, from an otherwise normally distributed process. To fit a folded normal distribution, only the average and specified sigma (process, sample, or population) are needed. Note that the standard normal curve generated will be used for K-S values and process capability, but that process sigma is always used to define the distribution limits on the Individual-X chart.
Learn more about the Statistical Inference tools for understanding statistics in Six Sigma Demystified (2011, McGraw-Hill) by Paul Keller, in his online Intro. to Statistics short course (only $89) or his online Black Belt certification training course ($875).