When testing hypotheses using two small samples,the t distribution may be used only after the additional assumption that
A)the populations means are equal.
B)the population variances are equal.
C)the population variances are not equal.
D)the population means are different.

Question

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When testing hypotheses using two small samples, the t-distribution may be used only after the additional assumption that the population variances are equal. This assumption is required for the calculation of the pooled variance used in the t-test formula. If the population variances are not equal, a modified version of the t-test called the Welch's t-test may be used instead. However, the Welch's t-test is less powerful than the traditional t-test when the population variances are equal. Therefore, it is preferable to assume equal variances unless there is evidence to the contrary.

When Testing Hypotheses Using Two Small Samples,the T Distribution May