It takes on the value 1 with the probability of 20% and the value of 0 with the probability of 80%.

等于1的概率是20%,等于0的概率是80%

耶鲁公开课 - 金融市场课程节选

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

耶鲁公开课 - 金融市场课程节选

We'll introduce in the next course angular nodes, but today we're just going to be talking about radial nodes, psi and a radial node is a value for r at which psi, and therefore, 0 also the probability psi squared is going to be equal to zero.

将会介绍角节点,但我们今天讲的是，径向节点，径向节点就是指，对于某个r的值,当然，也包括psi的平方，等于,当我们说到s轨道时。

麻省理工公开课 - 化学原理课程节选