Statistics for Six Sigma Made Easy

19.1. WHAT WE HAVE LEARNED IN CHAPTER 19

1. This chapter does not include a Six Sigma tool, but it does cover how someone can use data collected by many quality departments to compare with samples taken related to process trials or samples that are collected doing Six Sigma work.

2. Quality department systems often use child distributions, which are based on multiple sample averages, rather than the raw data itself. The raw data are often discarded after the average is calculated.

3. The sigma of the child distribution is always smaller than the sigma of the parent population, which is calculated using the raw data.

4. An estimate of the parent population sigma can be made by multiplying the child sigma by the square root of the individual child sample size. ...