If Two Populations Are Normally Distributed,the Sampling Distribution of the Difference

Multiple Choice

If two populations are normally distributed,the sampling distribution of the difference in the sample means, $\bar { X } _ { 1 } - \bar { X } _ { 2 }$ ,is:

A) approximately normal for any sample sizes.
B) approximately normal if both sample sizes are large.
C) exactly normal only if both sample sizes are large.
D) exactly normal for any sample sizes.