题目
You sample 25 observations from a sample of unknown variance. You calculate a sample mean of 70 and sample standard deviation of 60. You wish to conduct a two-tailed test of the null hypothesis that the mean is equal to 50. The most appropriate test statistic is a:
选项
A.z-statistic of 1.67
B.z-statistic of 0.33
C.t-statistic of 0.33 with 24 degrees of freedom
D.t-statistic of 1.67 with 24 degrees of freedom
答案
D
解析
Because the variance is unknown and the sample size is less than 30, the appropriate test statistic is a t-statistic with n-1=24 degrees of freedom. The t-statistic is (70-50)/(60/√25)=1.67 因为方差是未知的并且样本大小小于30，所以适当的检验统计量是n-1 =24自由度的t统计量。 t统计量为(70-50)/(60/√25)=1.67