z-transformation is an ubiquitous operation in data analysis. It is often quite practical. Example: Assume Dr Zack scored 42 points on a test (say, IQ). Average score is 40 in the relevant population, and SD is 1, let’s say. So Zack’s score is 2 points above average. 2 points equals to SDs in this example. We can thus safely infer that Zack is about 2 SDs above average (leaving measurement precision and other issues at …