document.write( "Question 62115This question is from textbook Elementary Statistics
\n" ); document.write( ": Among U.S. households, 24% have telephone answering machines. If a telemarketing campaign involves 2,500 households, find the probability that more than 650 have answering machines \n" ); document.write( "

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Among U.S. households, 24% have telephone answering machines. If a telemarketing campaign involves 2,500 households, find the probability that more than 650 have answering machines.
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\n" ); document.write( "The std deviation of the sample proportions is sqrt{pq/n)
\n" ); document.write( "=sqrt(0.24*0.76/2500)=0.008
\n" ); document.write( "The sample proportion is 650/2500=0.26
\n" ); document.write( "Convert 0.26 to a z-score,as follows:
\n" ); document.write( "z(0.26)=[0.26-0.24]/0.008=2.34
\n" ); document.write( "So, P(X>650)=P(z>2.34)=0.009 or 0.9%
\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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