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ditto · 2023年11月11日

A哪里不对

  1. CFA I
  2. Quantitative

NO.PZ2018062016000115

问题如下：

If analyst want to decrease the width of the confidence interval, which of the following statement should be selected.

选项：

A.

increase sample variance

B.

increase number of observations

C.

increase confidence level

解释：

B is correct, if number of observation become larger, sample variance is smaller, the width of confidence interval become smaller.

观察的次数越多，样本方差越小，置信区间的宽度越小。

confidence interval=point estimate ± reliability factor × standard error

如果方差变大， 标准差也会同乡变大， 上面公式里面的减数变大， 所以width变小， 那么A为什么会是错的

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1 个答案

星星_品职助教 · 2023年11月11日

同学你好，

上面公式是“±”，不是减。所以是加的数和减的数都变大，这就导致置信区间变宽。

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