posted by Teresa .
In a population of exam scores, a score of X = 48 corresponds to z = +1.00 and a score of X = 36 corresponds to z = -0.50. Find the mean and standard deviation of the population.
The difference between the 48 and the 36 is 1.5 standard deviations. Thus
1.5 sigma = 12,
and sigma (the standard deviation) = 8
48 is one sigma above the mean, so the mean is 40.