题目
MallRat is a real estate investment trust (REIT). During calendar year 2017, MallRat produced an average weekly (n = 52) return of +20 basis points with volatility of 19 basis points. Its benchmark during the same period produced an average return of +15 basis points. With 95.0% confidence, is the difference statistically significant?
选项
A.The result is different than the benchmark regardless of the test: the null is rejected in either a one-sided or two-sided test
B.The result is NOT different than the benchmark (accept null in two-sided test), but it is greater than the benchmark (reject null in one-sided test)
C.The result is different than the benchmark (reject null in two-sided test), but it is NOT greater than the benchmark (accept null in one-sided test)
D.The result is NOT different than the benchmark regardless of the test: the null is accepted in either a one- and two-sided test
答案
B
解析
The test statistic is given by (20 - 15)/[19/√52)] = 1.898. This is below 1.96 (the approximate two-tailed critical value) but above 1.65 (the approximate one-tailed critical value). Of course, 1.96 and 1.65 are the normal approximations for the exact student's t critical values of 2.008 (one-tailed) and 1.6753 (two-tailed) but the outcome is the same. 测试统计量（20 ? 15）/ [19 /√52）] = 1.898。 此值低于1.96（近似的两尾临界值），但高于1.65（近似的一尾临界值）。当然，精确的学生t临界值分别为2.008（一尾）和1.6753（两尾）的正常近似值为1.96和1.65，但结果是相同的。