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Unformatted text preview: l Estimation 0.7 ± .084
0.616 ≤ p ≤ 0.783 Example 2
The Canadian Education Association (CEA) recently proposed that their
union merge with the Canadian Federation of Teachers (CFT). The CEA
bylaws require that more than 2/3 of the membership must support any
such merger. A sample of 200 CEA members showed that 140
supported the merger. Develop a 99% confidence interval for the
proportion of the membership supporting the merger. Does it seem likely
that merger vote will pass?
α=.01; zα/2 = z0.005 =2.58; = 140/200 = 0.7; n = 200 p 99% Confidence interval: p ± zα 2
0.7 ± 2.58 p (1− p )
n
0.7⋅(1− 0.7)
200 Interval Estimation 0.7 ± .084
0.616 ≤ p ≤ 0.783 Or using MS Excel:
Lower: =.7–
NORM.S.INV(1–.01/2)*SQRT(.7*(1–.7)/200)=0.616533591
Upper:
=.7+NORM.S.INV(1–.01/2)*SQRT(.7*(1–.7)/200)=0.783466409 Example 2
The Canadian Education Association (CEA) recently proposed that their
union merge with the Canadian Federation of Teachers (CFT). The CEA
bylaws require that more than 2/3 of the membership must support any
such merger. A sample of 200 CEA members showed that 140
supported the merger. Develop a 99% confidence interval for the
proportion of the membership supporting the merger. Does it seem likely
that merger vote will pass?
α=.01; zα/2 = z0.005 =2.58; = 140/200 = 0.7; n = 200 p 99% Confidence interval: p ± zα 2
0.7 ± 2.58 p (1− p )
n
0.7⋅(1− 0.7)
200 Interval Estimation 0.7 ± .084
0.616 ≤ p ≤ 0.783 Or using MS Excel:
Lower: =.7–
NORM.S.INV(1–.01/2)*SQRT(.7*(1–.7)/200)=0.616533591
Upper:
=.7+NORM.S.INV(...
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This document was uploaded on 03/05/2014.
 Spring '13

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