Two independent samples of sizes 20 and 25 are randomly selected from two normal populations with equal variances. In order to test the difference between the population means, the test statistic is: $\begin{array}{|l|l|}
\hline A&\text {a standard normal random variable. }\
\hline B&\text { approximately standard normal random variable.}\
\hline C&\text {Student $ t $ distributed with 45 degrees of freedom. }\
\hline D&\text {Student $ t $ distributed with 43 degrees of freedom. }\
\hline
\end{array}$

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The Answer of Two independent samples of sizes 20 and 25 are randomly selected from two normal populations with equal variances. In order to test the difference between the population means, the test statistic is: $\begin{array}{|l|l|}
\hline A&\text {a standard normal random variable. }\
\hline B&\text { approximately standard normal random variable.}\
\hline C&\text {Student $ t $ distributed with 45 degrees of freedom. }\
\hline D&\text {Student $ t $ distributed with 43 degrees of freedom. }\
\hline
\end{array}$

Two Independent Samples of Sizes 20 and 25 Are Randomly