Another important concept in probability theory that we will use a lot is expected value, the mean, or average-- those are all roughly interchangeable concepts.

概率论中另外一个常用的重要的概念是,期望值或者也叫均值,这两个概念可以互换

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So, again we can use these probability density plots, which are just a plot of psi squared, where the density of the dots is proportional to the density, the probability density, at that point.

同样的我们可以利用这些概率密度图，这是psi的平方的图，这里面点的密度，正比于概率密度。

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