If it moves a lot--either way from the mean-- then this number squared is a big number.

如果距离均值的变动很大,那么这个平方数也会很大

耶鲁公开课 - 金融市场课程节选

What we want to do now is compute the mean and variance of the portfolio-- or the mean and standard deviation, since standard deviation is the square root of the variance-- for different combinations of the portfolios.

我们现在要做的是,计算这个投资组合的均值和方差-,或者均值和标准差，因为标准差的平方就等于方差-,这对任何投资组合都是一样的。

耶鲁公开课 - 金融市场课程节选

When we have n observations it's just the summation i = 1 to n of 2/n.

当有n个观察值,这就是在i取1到n时,x减去x均值的平方,除以n的累加

耶鲁公开课 - 金融市场课程节选