Suppose that a category of world-class runners are known to run a marathon (26 miles) in an average of 143 minutes with a standard deviation of 11 minutes. Consider 49 of the races. Let X^- bar the average of the 49 races.
a. X^-bar ~
b. Find the probability that the runner will average between 142 and 146 minutes in these 49 marathons.
c. Find the 80th percentile for the average of these 49 marathons.
d. Find the median of the average running times.