Question

An IQ test is designed so that the mean is 100 and the standard deviation is 21 for the population of normal adults. Find the sample size necessary to estimate the mean IQ score of statistics students such that it can be said with 95​% confidence that the sample mean is within 4 IQ points of the true mean. Assume that sigmaσequals=21 and determine the required sample size using technology. Then determine if this is a reasonable sample size for a real world calculation.

The required sample size is

Answer 1

We have given here,              
              
Population standard deviation =21
Margin of error =E=4
Level of significance =0.05
Z critical value is (by using Z table)=1.96
              
Sample size formula is

= 105.88

Therefore, sample size approximately will be 106