Mod note: This post was moved from another forum section, so doesn't use the homework template. A study of the amount of time it takes a mechanic to rebuild the transmission for a 2005 Chevrolet 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 8.7 hours. Is this the same as P(X-bar > 8.7) and P(Z > .16666666666..) because then the answer would be about 43% and the answers given are: 0.1469 0.1346 0.1946 0.1285 Can someone explain what I am doing wrong? Thanks in advance for your replies.