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%?