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.

Question

Quizplus · Accepted Answer

When the unknown population variances are equal, we can pool the sample variances to estimate the common variance of the two populations. This results in a more precise estimate of the standard error and a narrower confidence interval.

In Constructing a Confidence Interval Estimate for the Difference Between