Given the mean score on the test is 300 and the standard deviation is 30. What value on the test must a person score to be in the top 10%?

Answer 1

If we assume we have a normal distribution, we have the following formula.

mean + Z* standard deviation

Z is the Z score for the top 10%, so 90% or .90 fall below this score. From any Z table for the areas of a standard normal distribution, you find that Z = 1.28

Therefore the value on the test a person must score to be in the top 10% is

300 + 1.28(30)

300 + 38.4 = 338.4