By itself, the mean of an observed value can be misleading, especially at small sample sizes. The situation gets even murkier if you are trying to model two separate means (each with its own variance).

such as the Kolmogorov-Smirnov test, the meaning of which, I have to admit, I had forgotten. (It’s a way to determine whether a model correctly fits data.)

the analysis of big data using standard mathematical methods, such as regression analysis, results mostly in insights about correlation but not causation.