If Two Random Samples of Sizes $n _ { 1 }$

Short Answer

If two random samples of sizes $n _ { 1 }$ and $n _ { 2 }$ are selected independently from two populations with means $\mu _ { 1 }$ and $\mu _ { 2 }$ , then the mean of the sampling distribution of the sample mean difference, $\bar { X } _ { 1 } - \bar { X } _ { 2 }$ , equals: $$\begin{array} { | l | l | } \hline \text { A. } & \mu _ { 1 } + \mu _ { 2 } . \\\hline \text { B. } & \mu _ { 1 } - \mu _ { 2 } \\\hline \text { C. } & \mu _ { 1 } / \mu _ { 2 } \\\hline \text { D. } & \mu _ { 1 } \mu _ { 2 } \\\hline\end{array}$$ :