Posted by Lauran on .
the scores of a standardized test are normally distribution with a mean of 312 and a standard deviation of 68. The bottom 40% of scores are designed 'Need improvement'. What is the cutoff score for those who 'Need improvement'?
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the Z score related to the proportion (.40). Insert values into equation above to find the score.