为了使用这个公式来计算期望值你需要知道真实的概率值。
In order to compute using this formula you have to know the true probabilities.
事件发生的概率乘以事件的价值，就是该事件的期望值。
You take the probability of the event and multiply it times the value of that event and you have the expected value of that event.
图1：正态概率分布函数，它表明实际的观测值可能会偏离期望值(或者平均值)。
Figure 1: Normal probability density function, which illustrates that actual observations may vary from the expected (or average).
应用推荐