The level of cretaine phosphokinase (CPK) in blood samples measures the amount of muscle damage for athletes. At Jock State University, the level of CPK was determined for each of 25 football players...

The level of cretaine phosphokinase (CPK) in blood samples measures the amount of muscle damage for athletes. At Jock State University, the level of CPK was determined for each of 25 football players and 15 soccer players before and after practice. The two groups of athletes are trained independently. The data summary is as follows

Construct a 95% Confidence Interval for the difference in mean CPK values for football players BEFORE and AFTER exercises.

Test the claim that the mean CPK level has DECREASED for soccer players AFTER exercise (compared to the mean BEFORE exercise), using α=0.10.