A Coach Uses a New Technique in Training Middle Distance

Multiple Choice

A coach uses a new technique in training middle distance runners.The times for 9 different athletes to run 800 metres before and after this training are shown below. $$\begin{array}{l}\begin{array} {| l | llllllll l| } \hline \text { }&A&B&C&D&E&F&G&H&I\\\hline \text { Time before training (seconds) }&115.2&120.9&108.0&112.4&107.5&119.1&121.3&110.8&122.3\\\hline \text {Time after training (seconds) }&116.0&119.1&105.1&111.9&109.1&115.2&118.5&110.7&120.9\\\hline \end{array}\end{array}$$ Construct a 99% confidence interval for the mean difference of the "before" minus "after" times if $\overline { \mathrm { d } } ( \text { before } - \text { after } ) = 1.222 \text { and } \mathrm { s } _ { \mathrm { d } } = 1.826$ .

A) (-0.54,2.98)
B) (-6.42,8.87)
C) (-0.85,3.29)
D) (-0.76,3.20)
E) (-0.82,3.26)