(b) Estimate the sample size needed if no estimate of p is available. A sample of 504 adults is needed to obtain a 99.8% confidence interval with a margin of error of 0.03.

MATLAB: An Introduction with Applications
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Chapter1: Starting With Matlab
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Part two of the problem.  If no p is available, isn't 0.05 used?  Wouldn't it be:

0.05(1-0.05)(3.090/0.03)² 

How's the economy? A pollster wants to construct a 99.8% confidence interval for the proportion of adults who believe that economic conditions are getting
better.
Part 1 of 2
(a) A poll taken in July 2010 estimates this proportion to be 0.26. Using this estimate, what sample size is needed so that the confidence interval will have
a margin of error of 0.03?
A sample of 2.042 adults is needed to obtain a 99.8% confidence interval with a margin of error of 0.03.
Part: 1 / 2
Part 2 of 2
(b) Estimate the sample size needed if no estimate of p is available.
A sample of 504 Tadults is needed to obtain a 99.8% confidence interval with a margin of error of 0.03.
Transcribed Image Text:How's the economy? A pollster wants to construct a 99.8% confidence interval for the proportion of adults who believe that economic conditions are getting better. Part 1 of 2 (a) A poll taken in July 2010 estimates this proportion to be 0.26. Using this estimate, what sample size is needed so that the confidence interval will have a margin of error of 0.03? A sample of 2.042 adults is needed to obtain a 99.8% confidence interval with a margin of error of 0.03. Part: 1 / 2 Part 2 of 2 (b) Estimate the sample size needed if no estimate of p is available. A sample of 504 Tadults is needed to obtain a 99.8% confidence interval with a margin of error of 0.03.
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