what is the minimum sample size of adults that must be surveyed in order to be 9

Question

what is the minimum sample size of adults that must be surveyed in order to be 90% confident that the sample percentage is in error by no more than five percentage points assuming that 72% of the respondents believe that the economy is improving what is the minimum sample size of adults that must be surveyed in order to be 90% confident that the sample percentage is in error by no more than five percentage points assuming that 72% of the respondents believe that the economy is improving what is the minimum sample size of adults that must be surveyed in order to be 90% confident that the sample percentage is in error by no more than five percentage points assuming that 72% of the respondents believe that the economy is improving

Explanation / Answer

Note that      
      
n = z(alpha/2)^2 p (1 - p) / E^2      
      
where      
      
alpha/2 =    0.05  
       
      
Using a table/technology,      
      
z(alpha/2) =    1.644853627  
      
Also,      
      
E =    0.05  
p =    0.72  
      
Thus,      
      
n =    218.1750241  
      
Rounding up,      
      
n =    219   [ANSWER]

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