Nine Students Took the SAT $\mu _ { \mathrm { d } }$

Multiple Choice

Nine students took the SAT. Their scores are listed below. Later on, they took a test preparation course and retook the SAT. Their new scores are listed below. Construct a 95% confidence interval for $\mu _ { \mathrm { d } }$ Assume the
Samples are random and dependent, and the populations are normally distributed. $$\begin{array} { l | c c c c c c c c c } \text { Student } & 1 & 2 & 3 & 4 & 5 & 6 & 7 & 8 & 9 \\\hline \text { Scores before course } & 720 & 860 & 850 & 880 & 860 & 710 & 850 & 1200 & 950 \\\hline \text { Scores after course } & 740 & 860 & 840 & 920 & 890 & 720 & 840 & 1240 & 970\end{array}$$

A) (-30.50, -0.62)
B) (-20.34, 4.85)
C) (-10.32, 15.44)
D) (1.65, 30.59)