In testing the difference between two population means using two independent samples, we use the pooled variance in estimating the standard error of the sampling distribution of the sample mean difference if:
A) the sample sizes are both large.
B) the populations are normal with equal variances.
C) the populations are non-normal with unequal variances.
D) All of these choices are true.

Question

In testing the difference between two population means using two independent samples, we use the pooled variance in estimating the standard error of the sampling distribution of the sample mean difference  if:
A) the sample sizes are both large. 
B) the populations are normal with equal variances. 
C) the populations are non-normal with unequal variances. 
D) All of these choices are true.

Quizplus · Accepted Answer

When testing the difference between two population means using two independent samples, we use the pooled variance in estimating the standard error of the sampling distribution of the sample mean difference if the populations are normal with equal variances. If the sample sizes are both large, we can also use the pooled variance. If the populations are non-normal with unequal variances, we do not use the pooled variance.

In Testing the Difference Between Two Population Means Using Two