Construct a Confidence Interval for µD, the Mean of the Differences

Multiple Choice

Construct a confidence interval for µd, the mean of the differences d for the population of paired data. Assume that the population of paired differences is normally distributed.
-The table below shows the weights of 9 subjects before and after following a particular diet for two months. $\begin{array}{r|ccccccccc}\text { Subject } & \text { A } & \text { B } & \text { C } & \text { D } & \text { E } & \text { F } & \text { G } & \text { H } & \text { I } \\\hline \text { Before } & 168 & 180 & 157 & 132 & 202 & 124 & 190 & 210 & 171 \\\hline \text { After } & 162 & 178 & 145 & 125 & 171 & 126 & 180 & 195 & 163\end{array}$
Construct a $99 \%$ confidence interval for the mean difference of the "before" minus "after" weights.

A) $- 0.6 < \mu _ { \mathrm { d } } < 20.4$
B) $2.4 < \mu _ { \text {d } } < 17.4$
C) $2.8 < \mu _ { \mathrm { d } } < 17.0$
D) $4.51 < \mu _ { \mathrm { d } } < 15.7$