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pdf 83 正文55页 #207

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bizheyandebing opened this issue Dec 26, 2019 · 1 comment

bizheyandebing commented Dec 26, 2019

“如果协方差是正的，那么两个变量都倾向于同时取得相对较大的值。”
是否应修改为“如果协方差是正的，那么两个变量都倾向于同时取得相对较大的值或者同时取得相对较小的值。”

ssdreamC commented Dec 27, 2019 •

edited

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从协方差公式来看，如果两个变量都倾向于同时取得相对较大的值或者同时取得相对较小的值，那么函数值减去其期望倾向于同正或同负从而得到正的协方差。

但英文原文确实是“relatively high values simultaneously”：

If the sign of thecovariance is positive, then both variables tend to take on relatively high values simultaneously.

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