The Bureau of Alcohol Tobacco and Firearms BATF has been con

The Bureau of Alcohol, Tobacco, and Firearms (BATF) has been concerned about lead levels in California wines. Table 1 reports the results from a pilot test that measured lead levels in a random sampling of wines.

The BATF wishes to estimate the true average lead level for California wines to within 24 parts per billion at a 99% level of confidence? Based on the BATF\'s criteria, the number of wine specimens that should be tested is:  

Solution

Note that      
      
n = z(alpha/2)^2 s^2 / E^2      
      
where      
      
alpha/2 = (1 - confidence level)/2 =    0.005  
      
Using a table/technology,      
      
z(alpha/2) =    2.575829304  
      
Also,      
      
s = sample standard deviation =    120  
E = margin of error =    24  
      
Thus,      
      
n =    165.872415  
      
Rounding up,      
      
n =    166   [ANSWER]