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一丝不挂 · 2023年03月27日

我记得公式里面是除以n-1,这题为啥是除以n

NO.PZ2015120604000049

问题如下:

The table below shows the monthly stock returns of Ivy Corp.

According to the above tableCalculate the population variance for Ivy Corp. returns, assuming the population has 6 observations?

选项:

A.

8.01%.

B.

77.1%2.

C.

64.2%2.

解释:

C is correct

populationvariance=(Xμ)2npopulation\quad variance=\frac { { \sum { (X-\mu ) } }^{ 2 } }{ n }

=[(20- 7.7)2 + (4 - 7.7)2 + (-5 - 7.7)2 + (12- 7.7)2 + (3 - 7.7)2 + (12- 7.7)2] / 6 = 64.2%2



1 个答案

星星_品职助教 · 2023年03月28日

同学你好, 讲义中的公式基于的是“sample” variance,所以分母要调整为n-1。 本题要求计算的是“population”,所以分母就是原始的n本身。

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