Can you help me calculate the variance?

Question

Probability theory

Hello Terver experts! For the second day I have been struggling with one problem:

in the square 0<=x<=6 1<=y<=7, a point (X,Y) is randomly selected. It is necessary to calculate the dispersion of the value Z=XY.

Please help me decide how to approach it.

Answer 1

Normal article about variance on the wiki . Your version is the variance of a discrete random variable. Instead of mathematical expectation, the arithmetic mean is usually used.
It is more clearly described in the article about standard deviation . The variance is the square of the standard deviation. Well, i.e. in the standard deviation formula, you simply do not need to extract the last root.