Question

9. A county tax assessor wants to estimate within $125 the average property tax bill for county homeowners. If she wishes to be 90% confident, how large of a sample would be necessary if the population standard deviation is $600?

Answer 1

We have given here,                  
                  
Population standard deviation =   $600  
Margin of error =E=$125  
Level of significance =1-0.90=0.1  
Z critical value is (by using Z table)=1.645  
Sample size formula is                   
$n=\left [ \frac{Z*\sigma}{E} \right ]^{2}$
$=\left [ \frac{1.645*600}{125} \right ]^{2}$
=62.35

Sample size $\approx63$