You just need to familiarize yourself with the basic concepts of probability theory.

Mathematical expectation — in this case simply the average of the distribution function of a random variable.

Variance is a measure of the deviation from the mathematical expectation.

The standard deviation is root of variance.

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Obviously, if the second condition is running, you run first. Your task is just to understand what variance is and how it is calculated. Here it is in Wikipedia, for example.

It seems so.