document.write( "Question 366920: I am not sure how to solve this problem.
\n" ); document.write( "For their total production of light bulbs, the management of an electronics firm knows that the mean equals 150 hours. How large a sample is needed if they want to be 90% confident that the estimate of the average production time will be within 30 hours of the correct value? Does this have something to do with margin of error? \n" ); document.write( "
Algebra.Com's Answer #261540 by stanbon(75887)\"\" \"About 
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For their total production of light bulbs, the management of an electronics firm knows that the mean equals 150 hours. How large a sample is needed if they want to be 90% confident that the estimate of the average production time will be within 30 hours of the correct value? Does this have something to do with margin of error?
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\n" ); document.write( "Yes.
\n" ); document.write( "Since ME = z
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\n" ); document.write( "sqrt(n) = z*s/ME
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\n" ); document.write( "n = [zs/ME]^2
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\n" ); document.write( "Your Problem:\r
\n" ); document.write( "\n" ); document.write( "n = [1.645s/30]^2 where s is the standard deviation of the population.
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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