Question

2. [4 points] Serum cholesterol levels were monitored to investigate the effect of physical training. Prior to this training, blood samples were acquired from each of the 12 subjects and were tested for cholesterol level. After a week-long training period of daily running, the same individuals were retested, yielding the following data:
PRE-TRAINING
182
232
191
200
148
249
276
213
241
480
262
189
SUBJECT
POST-TRAINING
A 198
B 210
C 194
D 220
E 138
F 220
G 219
H 161
I 210
J 313
K 226
L 202
Compute a 90% confidence interval for the mean decrease of cholesterol level after physical training. You do not need to calculate any standard deviations by hand—feel free to use a calculator or spreadsheet for this.
[Be careful: you are being asked for the mean decrease, not the decrease of the mean! You may assume n-1 degrees of freedom, and will need to estimate a value of t from your table.]