The Bureau of Alcohol, Tobacco, and Firearms (BATF) has been concerned about lea

Question

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 18 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:

Explanation / Answer

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 =    210  
E = margin of error =    18  
      
Thus,      
      
n =    903.0831485  
      
Rounding up,      
      
n =    904   [ANSWER]

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