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Unformatted text preview: Election polls For each race, we have one or more polls reported as ¯ X ± 2SE, or “ ¯ X with a margin of error of ME.” Typical ME’s are 0.03-0.04. In our notation, ME = 2SE. The data underlying ¯ X are X 1 , .. . , X n , which are binary variables where X i = 1 corresponds to support for one candidate and X i = 0 corresponds to support for the other candidate. If the poll is a simple random sample, ME = 2 · SE = 2 p EX · (1- EX ) / n Solve for n : n = 4 EX · (1- EX ) / ME 2 . If EX = 1 / 2, and ME = 0 . 03, then n ≈ 1100. 1 / 9 Bias in election polls Ideally, EX is the result that will occur in the actual election (since the election is a poll with huge sample size). In reality, it’s more complicated for at least three reasons: I People may change their mind between the time that the poll is conducted and the time of the election. I People may not respond honestly in the poll....
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This note was uploaded on 02/06/2012 for the course STAT 403 taught by Professor Kerbyshedden during the Winter '12 term at University of Michigan-Dearborn.
- Winter '12