The average score on a particular exam is determined to be 84.35 with a standard deviation of 7.4. Assume the scores are normally distributed. Applicants with exam scores in the lower 10% directed to special retraining.
What is the minimum score required not to be directed to retraining?
You want the highest 90%.
Z = (score-mean)/SD
Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion. Use that Z score in the above equation. (Remember that the Z score will be negative.)