See #6 in this thread: http://www.mathhelpforum.com/math-he...ssistance.html
A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 chevy cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours.
If 40 mechanics are randomly selected, find the probability that their mean rebuild time exceeds 9.1 hours.
See #6 in this thread: http://www.mathhelpforum.com/math-he...ssistance.html