posted by Sav .
The lifetime of a SuperTough AAA battery is normally distributed with mean of 28.5 hours and standard deviation of 5.3 hours. For a battery selected at random, what is the probability that the lifetime will be 34 hours or less?
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to the Z score.