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Unformatted text preview: UF-ESI-6321 UF-ESI-6321-04-10.xmcd page 1 of 1 4.10 During a local election between two candidates, exit polls based on a sample of n := 400 voters indicated that pbar := 54 % of the voters supported the incumbent candidate. (a) Construct a 98% confidence interval for the percentage of votes that the incumbent has received in this election. Z98 := 2.326 p bar ( 1 - p bar ) n upper := pbar + Z98 upper = 0.60 pbar ( 1 - p bar ) n lower := p bar - Z98 lower = 0.48 Note that n p bar 5 = 1 n ( 1 - p bar ) 5 = 1 (true) (true) which makes this analysis valid per page 171 of the textbook. (b) How large a sample is required in order to declare the incumbent candidate a winner at the 99% confidence level? The currently measured 54% support for the incumbent allows an error range up to, but not including, 4%. L := 4% c := 2.576 n := ceil c2 = 1037 4 L2 Luther Setzer 1 NASA Pkwy E Stop NEM3, Kennedy Space Center, FL 32899 (321) 544-7435 ...
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- Spring '07