For example, a city has 65,438+10,000 families, 65,438+10,000 families have no children, 90,000 families have one child, 6,000 families have two children, and 3,000 families have three children.
Then the number of children in any family in this city is a random variable, marked X, which can be 0, 1, 2, 3, where the probability of taking 0 is 0.0 1, the probability of taking 1 is 0.9, the probability of taking 2 is 0.06, and the probability of taking 3 is 0.03. Its mathematical expectation is 0× 0.01+/kloc-0 /× 0.9+2× 0.06+3× 0.03, which is equal to 1. 1 1, that is, the average family in this city is1.
In other words, we analyzed this probability problem with mathematical methods. For every family, it is most likely to have 1. 1 1 children.
You can simply understand the average situation of a probability event.