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 non-normally distributed populations, then the sampling distribution of the sample mean difference, $\bar { X } _ { 1 } - \bar { X } _ { 2 }$ , is: $\begin{array}{|l|l|}\hline A&\text {always non-normal. }\\\hline B&\text {always normal. }\\\hline C&\text {approximately normal only if \( n_{1} \) and \( n_{2} \) are both larger than 30 . }\\\hline D&\text {approximately normal regardless of \( n_{1} \) and \( n_{2} \). }\\\hline \end{array}$