The Expected Value of the Difference of Two Sample Means

Short Answer

The expected value of the difference of two sample means equals the difference of the corresponding population means: $\begin{array}{|l|l|}\hline A&\text {only if the populations are normally distributed. }\\\hline B&\text { only if the samples are independent.}\\\hline C&\text { only if the populations are approximately normal and the sample sizes are large.}\\\hline D&\text {All of these choices are correct. }\\\hline \end{array}$