So if you look at the entire distribution like this, this is the mean right over here.

所以如果你像这样看整个分布，这就是这里的平均值。

So this is the sum over the entire probability distribution, and so that is going to be equal to 1.

所以这是整个概率分布的总和，所以它等于 1。

Because the area under the entire normal distribution is 100, or 100%, or 1, depending on how you want to think about it.

因为整个正态分布下的面积是100， 或者100%，或者1，就看你怎么想了。