Question

The parent population mean grade, μ, on a final exam was 81, and the parent population standard deviation, σ, was 10. The instructor grades such that only the top 10% of the class receives an A on the final exam, assuming the grades follow a normal distribution (assumed because the number of students is seemingly infinite). What is the minimum grade necessary to make an A on the final?

Answer 1

Given that,

P(Z > 1.28) = 0.10

z = 1.28

Using z-score formula,

x = z * +

x = 1.28 * 10 + 81 = 93.8

minimum grade = 93.8