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shuangzili · 2021年11月30日

可以从头到尾计算一遍吗？

  1. CFA I
  2. Quantitative

NO.PZ2015120604000137

问题如下：

Ida Lee and his team collect a lot of analysis of statistical data about the car market .According to the data, they come to the conclusion that the mean price of SUV is more than $46,435 in his country. Then they randomly select 64 SUVs whose mean price is $46,760. Assuming the standard deviation of the sample is 1370. Ida Lee conducts a hypothesis test to check their conclusion. At which significant level should Ida Lee reject the null hypothesis?

选项：

A.

0.5%.

B.

5%.

C.

1%.

解释：

B is correct.

If the significant level is 5%, the critical value=1.669<1.8978, Ida Lee should reject the null.

If the significant level is 0.5%, the critical value=2.656>1.8978, Ida Lee will fail to reject the null.

If the significant level is 1%, the critical value=2.387>1.8978, Ida Lee will fail to reject the null.


可以从头到尾计算一遍吗？ 非常感谢。算出来的数是1.92 330/1370/根号63 是1.92
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2 个答案

星星_品职助教 · 2021年12月02日

@shuangzili

最简单的方法就是直接跟着公式走。公式里是n就代入n。

从理解的角度出发，分母要代入的是样本均值（X bar）的标准差，也就是标准误。根据中心极限定理，样本均值的标准差 为总体标准差σ（σ未知时用样本标准差s替代）除以根号n，并不是n-1。

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只有在计算样本标准差时才会分母用n-1。也就是说如果此时要计算s，s的公式里分母是n-1.

星星_品职助教 · 2021年11月30日

同学你好，

这道题目的计算代入t统计量的公式即可。代入后计算结果为：(46760-46435)/(1370/√64)=1.8978。

从你的列式来看，分子应为325；分母应为根号下64，而非n-1后的63.


shuangzili · 2021年12月01日

是随机抽取的样本，请问样本的话不是➗n-1吗？

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