Statistical formulas that programmers should master

Evan Miller collected the statistical formula that programmers should master: http://www.evanmiller.org/statistical-formulas-for-programmers.html
Very useful.

However, his remarks earlier in the article are more instructive:
Being able to use statistics is like having a secret super power.
Most people only look at the average, and you will look at the confidence interval.
If others say "7 to 5", you will say that the process of generating data cannot be identified.
In the noble noise, you will hear the key help.

Unfortunately, not many programmers have this super power. This is really a tragedy, because the use of statistics can almost always improve the presentation and interpretation of data. Therefore, I have collected statistical formulas that I think are the most useful.