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

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That has moved around a lot, but it got almost up to 60% in the post World War II period and now it's down to less than a third.

计算所得的百分率变动很大,二战后,它一度达到将近60%,现在又降到不到三分之一

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If they tend to move together, when x is high and y is high together at the same time, then the covariance will tend to be a positive number.

如果x和y同向变动,当x值和y值同时都很大,协方差的结果将会是一个正值

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