SOLUTION: A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.04 wi

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Question 1133246: A researcher wishes to estimate the proportion of adults who have​ high-speed Internet access. What size sample should be obtained if she wishes the estimate to be within 0.04 with 90​% confidence if
​(a) she uses a previous estimate of 0.58​?
​(b) she does not use any prior​ estimates?
Answer by rothauserc(4718) About Me  (Show Source):
You can put this solution on YOUR website!
Margin of Error(ME) = 0.04
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critical statistic(z) for a 90% confidence level is 1.645
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when standard deviation is not known, we use
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sample size n = p*(1-p)*(z/ME)^2, where p is the proportion
:
a) n = 0.58 * (1-0.58)*(1.645/0.04)^2 = 411.9923
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sample size is 412
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b) p is not known, so use p = 0.50
:
n = 0.50 * (1-0.50)*(1.645/0.04)^2 = 422.8164
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sample size is 423
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