statistics
posted by roy .
suppose that grade point averages of undergraduate students at one university have a bell shaped distribution with a mean of 2.55 and a standard deviation of 0.43. Using the empirical rule, what percentage of students have grade point averages that are between 1.26 and 3.84

Z = (scoremean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion/probability between the two Z scores.