document.write( "Question 491599: A federal
\n" ); document.write( "report stated that 88% of children under age 18 were
\n" ); document.write( "covered by health insurance in 2000. How large a
\n" ); document.write( "sample is needed to estimate the true proportion of
\n" ); document.write( "covered children with 90% confidence with a
\n" ); document.write( "confidence interval 0.05 wide?
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Algebra.Com's Answer #334732 by stanbon(75887)\"\" \"About 
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A federal
\n" ); document.write( "report stated that 88% of children under age 18 were
\n" ); document.write( "covered by health insurance in 2000. How large a
\n" ); document.write( "sample is needed to estimate the true proportion of
\n" ); document.write( "covered children with 90% confidence with a
\n" ); document.write( "confidence interval 0.05 wide?
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\n" ); document.write( "If the CI is 0.05 wide
\n" ); document.write( "2E = 0.05
\n" ); document.write( "E = 0.025
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\n" ); document.write( "Since E = z*sqrt(pq/n)
\n" ); document.write( "sqrt(n) = [z/E]*sqrt(pq)
\n" ); document.write( "---
\n" ); document.write( "So, n = [z/E]^2*pq
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\n" ); document.write( "n = [1.645/0.025]^2*0.18*0.72
\n" ); document.write( "---
\n" ); document.write( "n = 562 when rounded up
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.\r
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