Mathematical expectation is an important numerical feature, which reflects the average value of random variables and is the sum of the probabilities of each possible result multiplied by its result in the experiment. The word "expectation" here comes from gambling, which probably refers to how much money you expect to win when you bet.

Expectation is not necessarily equal to "expectation" in common sense-expectation is not necessarily equal to every result. The expected value is the average of the output values of variables. The expected value is not necessarily contained in the set of output values of variables.

Extended data

Application:

1, random stock trading

Random stock picking is to pick a stock in the stock market with your eyes closed. Assuming that both the stop loss line and the take profit line are 10%, because it is random stock picking, the winning rate is equal to the loss rate, and because of stamp duty, commission and handling fee, the winning rate is equal to the loss rate.

3. Value investment

Because the value is underestimated and the winning rate is relatively high, a margin of safety is reserved for value investment, that is, the upward space is huge and the downward space is limited, so the expected value of mathematics must be positive.

Baidu Encyclopedia-Mathematical Expectation