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大马勺 · 2021年01月28日

b选项

NO.PZ2018062016000140

问题如下:

During the table below, the mean monthly return of X Index in the first five years have been different than the mean return in the second five years.

Let the μ1 stand for the population mean return for the year1 through year 5 and μ2 stand for the population mean return for the year 6 through year 10, the following hypothese: H0: μ1 – μ2 = 0 versus Ha: μ1 – μ2 ≠ 0

Assume that the significant level is 0.05

Which of the following options is most accurate?

选项:

A.

The null hypothesis will be rejected if t<-1.98 or t>1.98.

B.

The t-test has 119 degrees of freedom.

C.

The rejection points are ±1.658.

解释:

A is correct. The two samples are drawn from two different time periods, so they are independent samples. The population variances can be assumed to be equal. Under all considerations, the t-test has 60+60-2=118 degrees of freedom.For a two-tailed test, at the significant level of 0.05, the rejection points are ±1.980, so we will reject the null if t<-1.980 or t>1.980.

b选项中“自由等级”如何理解?

2 个答案
已采纳答案

星星_品职助教 · 2021年01月29日

@大马勺

这里的自由度计算是60+60-2=118。各个检验的自由度可以参照一下讲义里的这张图。

星星_品职助教 · 2021年01月29日

同学你好,

“degrees of freedom”是自由度的意思。不同的检验对应不同的自由度,这个需要记忆一下的。

 

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