Question

Dear Math Helper, You write a great column, and I hope you stay around for years to come. I run a small boarding school. We are going to begin using test scores to help determine admissions eligibility. The scores for the test I have in mind are normally distributed with a mean of 300 and a standard deviation of 12.5. Can you show me how to determine the cutoff score if we should use to only accept only applicants who score in the top 10% on the test? What cutoff score includes the top 15%? Thanks in advance. Regards, The Student Selector

Answer 1

The easiest way to determine the score is to use a calculator or spreadsheet and the appropriate probability function.

If you want the top 10%, the score corresponds to the 90th percentile. That score is 316.

If you want the top 15%, the score corresponds to the 85th percentile. That score is 313.