posted by kevin on .
The mean score on a Math exam was 50% and the standard deviation was 10%. Assume the results were normally distributed.
(a) What percent of students earned a score between 50% and 70%?
(b) If 60 students took the exam, how many got a score between 50% and 70%?
Z = (x - μ)/SD
Z = (x -50)/10
a) Get the respective Z scores. Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion between the two Z scores.
b) Multiply the proportion above by 60.