In Constructing a Confidence Interval Estimate for the Difference Between

Multiple Choice

In constructing a confidence interval estimate for the difference between the means of two normally distributed populations, using two independent samples, we:

A) pool the sample variances when the unknown population variances are equal.
B) pool the sample variances when the population variances are known and equal.
C) pool the sample variances when the population means are equal.
D) never pool the sample variances.