(New page: p = fraction supporting McCain To find p, ask 1000 people who they support. declare answer = # supp Mc / 1000 = X / 1000 X = # supp Mc in poll X is binomal(1000,p) E[X] = 1000*p Var(...) |
(No difference)
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Revision as of 12:03, 2 November 2008
p = fraction supporting McCain
To find p, ask 1000 people who they support.
declare answer = # supp Mc / 1000 = X / 1000
X = # supp Mc in poll
X is binomal(1000,p)
E[X] = 1000*p
Var(X) = 1000*p*(1-p)
Pr[ |(X/1000) - p | >= 0.1 ]
= Pr[ | X - 1000*p | >= 1000 ]
<= Var(X)/100^2
= 1000*p*(1-p)/100^2
= p*(1-p)/10
Pr[ | (X/1000) - p | >= 0.1 ] <= (1/4)/10 = 1/40
