单选题
In a two - tailed hypothesis test, Jack Olson observes a t - statistic
of -1.38 based on a sample of 20 observations where the population mean is zero.
If you choose a 5 percent significance level, you should:
- A. reject the null hypothesis and conclude that the population mean is
significantly different from zero.
- B. fail to reject the null hypothesis that the population mean is not
significantly different from zero.
- C. reject the null hypothesis and conclude that the population mean is not
significantly different from zero.
【正确答案】
B
【答案解析】At a 5 percent significance level, the critical t - statistic using the Student's t-distribution table for a two - tailed test and 19 degrees of freedom ( sample size of 20 less 1 ) is ±2.093 ( with a large sample size the critical Z - statistic of 1. 960 may be used). Because the critical t - statistic of -2.093 is to the left of the calculated t - statistic of -1.38, meaning that the calculated t-statistic is not in the rejection range, we fail to reject the null hypothesis that the population mean is not significantly different from 0.