Question

A set of 1,000 values has a normal distribution. The mean of the data is 120, and the standard deviation is 20.
Find the limit below which 90% of the data lie.

Answer 1

so to find 90% you find 90% on a normal distrib. curve which is a z score of 1.29. so the equation is: x-120 / 20 =1.27 so you would need 145.4 and 90% under lie under that point