A professor at a local college noted that the grades of his students were normally distributed with an average percentage of 74 and a population standard deviation of 10. He found that 6.3% of his students received A's while 2.5% of his students failed the course and received F's. Based upon the professor's grading scale, what was the minimun percentage needed to get an A in the course?

Question

A professor at a local college noted that the grades of his students were normally distributed with an average percentage of 74 and a population standard deviation of 10.  He found that 6.3% of his students received A's while 2.5% of his students failed the course and received F's.  Based upon the professor's grading scale, what was the minimun percentage needed to get an A in the course?

PsyDAG · Answer

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 your proportion. Put that value along with the values of mean and SD to find the score.