A research company desires to know the know consumption of m

A research company desires to know the know consumption of milk per week among males over age 45. They believe that the milk consumption has a mean of 4.5 liters, and want to construct a 95% confidence interval with a maximum error of 0.08 liters. Assuming a variance of 1 liters, what is the minimum number of males over age 45 they must include in their sample?

Solution

Note that      
      
n = z(alpha/2)^2 s^2 / E^2      
      
where      
      
alpha/2 = (1 - confidence level)/2 =    0.025  
      
Using a table/technology,      
      
z(alpha/2) =    1.959963985  
      
Also,      
      
s = sample standard deviation =    1  
E = margin of error =    0.08  
      
Thus,      
      
n =    600.2279407  
      
Rounding up,      
      
n =    601   [ANSWER]