单选题 A test of a hypothesis that the means of two normally distributed populations are equal based on two independent random samples:

A. is based on a Chi Square statistic.
B. is a paired -comparisons test.
C. is done with a t -statistic.

【正确答案】 C

【答案解析】We have two formulas for test statistics for the hypothesis of equal sample means. Which one we use depends on whether or not we assume the samples have equal variances. Either formula generates a test statistic that follows a T- distribution.