8.3 Estimation Proportion

# P 05 z2 z0025 196 220500 044 n 500 95 confidence

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Unformatted text preview: population of the registered voters that favour the candidate. p α=.05; zα/2 = z0.025 =1.96; = 220/500 = 0.44; n = 500 95% Confidence interval: p ± zα 2 p ( 1n− p ) 0.44 ± 1.96 0.44⋅( 1− 0.44 ) 500 Interval Estimation 0.44 ± 0.04351 0.3965 ≤ p ≤ 0.4835 Example 1 Political Science, Inc. (PSI) specializes in voter polls and surveys designed to keep political office seekers informed of their position in a race. In a current election campaign, PSI has just found that 220 registered voters, out of 500 surveyed, favour a particular candidate. PSI wants to develop a 95% confidence interval estimate for the proportion of the population of the registered voters that favour the candidate. p α=.05; zα/2 = z0.025 =1.96; = 220/500 = 0.44; n = 500 95% Confidence interval: p ± zα 2 p ( 1n− p ) 0.44 ± 1.96 0.44⋅( 1− 0.44 ) 500 Interval Estimation 0.44 ± 0.04351 0.3965 ≤ p ≤ 0.4835 Or using MS Excel: Lower: =.44– NORM.S.INV(1–.05/2)*SQRT(.44*(1–.44)/500)=0.396490565 Upper: =.44+NORM.S..NV(1–.05/2)*SQRT(.44*(1–.44)/500)=0.483509435 Example 1 Political Science, Inc. (PSI) specializes in voter polls and surveys designed to keep political office seekers informed of their position in a race. In a current election campaign, PSI has just found that 220 registered voters, out of 500 surveyed, favour a particular candidate. PSI wants to develop a...
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## This document was uploaded on 03/05/2014.

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