Question

Standard normal distribution question!!. assume that adults have IQ scores that are normally distributed with a mean of 100 and a standard deviation 20. Find P15, which is the IQ score separating the bottom 15% from the top 85%

Answer 1

The 15th percentile (area below which 15 % of cases lie in a standard normal distribution is, from tables -1.04 
z=(x-mean)/sd 
-1.04 = (x-100)/15 
x=100+15(-1.04) =84.4