In Testing Whether the Means of Two Normal Populations Are

Multiple Choice

In testing whether the means of two normal populations are equal,summary statistics computed for two independent samples are as follows: $$\begin{array} { | c | c | } \hline \text { Brand } \boldsymbol { X } & \text { Brand } \boldsymbol { Y } \\\hline n _ { 1 } = 25 & n _ { 2 } = 25 \\\bar { x } _ { 1 } = 7.30 & \bar { X } _ { 2 } = 6.80 \\s _ { 1 } = 1.05 & s _ { 2 } = 1.20 \\\hline\end{array}$$ Assume that the population variances are equal.Then,the standard error of the sampling distribution of the sample mean difference $\overline { \mathrm { x } } _ { 1 } - \overline { \mathrm { x } } _ { 2 }$ is equal to:

A) 0.1017.
B) 1.2713.
C) 0.3189.
D) 1.1275.