Question

A fashion designer wants to know how many new dresses women buy each year. Assume a previous study found the standard deviation to be 1.4. She thinks the mean is 7.3 dresses per year. What is the minimum sample size required to ensure that the estimate has an error of at most 0.13 at the 90% level of confidence? Round your answer up to the next integer.

Answer 1

We have given here,              
              
Population standard deviation =   1.4
Margin of error =E=0.13
Level of significance =1-0.90=0.1
Z critical value is (by using Z table)=1.645
Sample size formula is               


=313.83  

Sample size