Ten Different Families Are Tested for the Number of Gallons

Multiple Choice

Ten different families are tested for the number of gallons of water a day they use before and after viewing a conservation video.Construct a 90% confidence interval for the mean of the differences.

$\begin{array}{|l|l|l|l|l|l|l|l|l|l|l|}\hline \text { Before } & 33 & 33 & 38 & 33 & 35 & 35 & 40 & 40 & 40 & 31 \\\hline \text { After } & 34 & 28 & 25 & 28 & 35 & 33 & 31 & 28 & 35 & 33 \\\hline\end{array}$

A) $( 1.8,7.8 )$
B) $( 2.5,7.1 )$
C) $( 3.8,5.8 )$
D) $( 1.5,8.1 )$
E) $( 2.1,7.5 )$