Seven Randomly Selected Plants That Bottle the Same Beverage Implemented $\mu _ { d }$

Multiple Choice

Seven randomly selected plants that bottle the same beverage implemented a time management program in hopes of improving productivity. The average time, in minutes, that it took the companies to produce the same quantity of bottles before and after the program are listed below. Assume the two population distributions are normal. Construct a 90 % confidence interval for $\mu _ { d }$ Assume that the paired data came from a population that is normally distributed.
$\begin{array} { l | c c c c c c c } \text { Plant } & 1 & 2 & 3 & 4 & 5 & 6 & 7 \\\hline \text { Before } & 75 & 89 & 31 & 90 & 120 & 50 & 40 \\\hline \text { After } & 70 & 80 & 30 & 85 & 100 & 49 & 42\end{array}$

A) (0.21,10.93)
B) (1.60,9.54)
C) (-0.22,11.36)
D) (-22,33.3)