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vee · 2022年11月09日

不懂

  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.


1.669

2.656怎么得到的，critical value什么意思

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vee · 2022年11月09日

是因为t分布表格得到的吗，看了一遍视频，好像明白了

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已采纳答案

星星_品职助教 · 2022年11月09日

同学你好，

1.669、2.656、2.387都是critical value的概念，即拒绝域在横轴上所对应的关键值。critical value（关键值）都是查表（本题为t分布）得到的 。

如果计算出来的test statistic的绝对值 大于了 查表得到critical value的绝对值，则拒绝原假设。



_ Steven _ · 2023年05月28日

请问这题如何知道是差T分布表？如果是查T分布表题干也没有说明自由度是多少，请问如何查表？谢谢。我算出了1.8978，也选对了。但是对这里如何查对表很疑惑。

星星_品职助教 · 2023年05月28日

@ Steven _

1）本题里没有给出总体方差/标准差。根据“总体方差未知，用t分布”确定应该查t表。

2）本题为检验均值和一个确定的数字之间的关系。这个场景下的t分布自由度是n-1。可见教材截图：

由于n=64（they randomly select 64 SUVs），所以需要根据自由度为63来查表（但教材提供的t表没有63的数字，所以最后实际是根据最接近的自由度60来查的）。

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