This paper discusses classical model,formula of total probability,normal distribution,mathematic expectation and the central limit theorem.

The thesis sets up the ready-made flour-product sale profit model by putting forward the conditions on which the maximum mathematic expectation of profit is based.

This article is mainly on the basis of the binomial distribution,the multinomial distribution,in the negative binomial distribution foundation to promote the negative binomial distribution fatherly,to give the negative term distributed definition,to infer its probability distribution and to calculate its mathematic expectation and the variance.

A calculation for random variable mathematical expectation;

On direct methods to the mathematical expectation and variance in the matching problem

In this paper,we give a quantitative representation of the ability of knowledge′s classification,and provide a novel representation of knowledge,that is,it can be expressed by expectation.

The formula of expectation of symmetric distribution is proved,some examples are give

Based on random variable expectation and variance, some inequalities are proved.

This paper introduced the appliance of probability and statistics in reality,including classical model,formula of total probability, normal distribute,mathematics expectation and the central limit theorem.

Based upon related theories and his own teaching experience, the authors of this paper give several methods about the calculation of discrete random variable mathematics expectation.