document.write( "Question 98165: If 20% of the residents in Washington prefer a white telephone over any other color available,
\n" ); document.write( "what is the probability that among the next 1000 telephone installed in the city
\n" ); document.write( "i) between 170 and 185 inclusive will be white
\n" ); document.write( "ii) at least 210 but not more than 225 will be white \n" ); document.write( "
Algebra.Com's Answer #71463 by stanbon(75887)\"\" \"About 
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If 20% of the residents in Washington prefer a white telephone over any other color available,
\n" ); document.write( "what is the probability that among the next 1000 telephone installed in the city
\n" ); document.write( "i) between 170 and 185 inclusive will be white
\n" ); document.write( "It's a binomial problem that requires a normal approximation answer.
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\n" ); document.write( "With p=0.20 and n=1000, mean=np = 200; std. dev. = sqrt(npq)=sqrt(160) = 4sqrt10
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\n" ); document.write( "Find the z-score of 170 and the z-score of 185
\n" ); document.write( "Find the area under the normal curve over the interval between those two z-values
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\n" ); document.write( "ii) at least 210 but not more than 225 will be white
\n" ); document.write( "Find the z score for 210 and for 225
\n" ); document.write( "Find the area between those two z scores
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H. \n" ); document.write( "
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