A researcher wishes to estimate the percentage of adults who support abolishing the penny. What size sample should be obtained if he wishes the estimate to be within 3 percentage points with 95% confidence if (a) he uses a previous estimate of 32%?

(b) he does not use any prior estimates?

a)  

And rounded up we have that n=929

b)  

And rounded up we have that n=1068

Step-by-step explanation:

Part a

The margin of error for the proportion interval is given by this formula:  

   (a)  

And on this case we have that and we are interested in order to find the value of n, if we solve n from equation (a) we got:  

  (b)  

For a confidence of 95% we have that the significance is and the critical value would be:

And replacing into equation (b) the values from part a we got:

And rounded up we have that n=929

Part b

For this case since we don't have prior info we can use as estimator for the true proportion the value and replacing we got:

And rounded up we have that n=1068

answer: the answer is 84.

step-by-step explanation: i just answered it and 84 is correct. look at the graph and it should be the number between 2 points on the graph.