January 7, 2010
A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier sh?
cassandra d asked:
A study of the amount of time it takes a mechanic to rebuild the transmission for a 1992 Chevrolet Cavalier shows that the mean is 8.4 hours and the standard deviation is 1.8 hours. If a mechanic is randomly selected, find the probability that the mean rebuild time is less than 7.6 hours.
z value = (7.6 - 8.4)/1.8 = - 0.44
A reference to normal distribution tables gives
P(rebuild time < 7.6 hours) = 33%
(If greater accuracy than two decimal places is needed, interpolation can be done)