expected value of a probability distribution

例句：

1. 1.The expected value of the population is calculated using the formula.
   使用公式计算人口的期望值。
2. 2. The expected value of the stock price has increased by 5%.
   股票价格的预期值增加了5%。
3. 3. The expected value of a probability distribution is the sum of all possible outcomes divided by the number of outcomes.
   概率分布的期望值是所有可能结果的和除以可能结果的数量。