1.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

B)   is a paired-comparisons test.

C)   is done with a t-statistic.

D)   can only be done if the sample variances are equal.

答案和详解如下：

1.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

B)   is a paired-comparisons test.

C)   is done with a t-statistic.

D)   can only be done if the sample variances are equal.

The correct answer was C)

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.