Data Set Here are the IQ test scores of 31 seventhgrade girl

Data Set

Here are the IQ test scores of 31 seventh-grade girls in a Midwest school district: Data Set

Solution

sample mean= 105.8387

sample standard deviation= 14.27141

Given a=1-0.8=0.2, Z(0.1) =1.28 (from standard normal table)

So the lower bound is

xbar - Z*s/vn = 105.8387 -1.28*14.27141/sqrt(31) =102.5578

So the upper bound is

xbar + Z*s/vn = 105.8387 +1.28*14.27141/sqrt(31) =109.1196

Answer: A102.39 to 109.29