单选题

Using the sample results given below, drawn as 25 paired observations from their underlying distributions, test if the mean returns of the two portfolios differ from each other at the 1% level of statistical significance. Assume the underlying distributions of returns for each portfolio are normal and that their population variances are not known.

	Portfolio 1	Portfolio 2	Difference
Mean Return	17.00	21.25	4.25
Standard Deviation	15.50	15.75	6.25
t-statistic for 24 df and at the 1% level of statistical significance=2.807

Based on the paired comparisons test of the two portfolios, the most appropriate conclusion is:

A、 reject the hypothesis that the mean difference equals zero as the computed test statistic exceeds 2.807.
B、 accept the hypothesis that the mean difference equals zero as the computed test statistic exceeds 2.807.
C、 accept the hypothesis that the mean difference equals zero as the computed test statistic is less than 2.807.

【正确答案】 A

【答案解析】

The test statistic is:
, whereis the mean differenceis the hypothesized difference in the means, is the sample standard deviation of differences, and n is the sample size. In this case, the test statistic equals: (4.25 - 0) / (6.25 /