document.write( "Question 1142560: Managers at an automobile manufacturing plant would like to estimate the mean completion time of an assembly line operation, μ. The managers plan to choose a random sample of completion times and estimate μ via the sample. Assuming that the standard deviation of the population of completion times is 10.1 minutes, what is the minimum sample size needed for the managers to be 99% confident that their estimate is within 1.7 minutes of μ? \n" ); document.write( "

Algebra.Com's Answer #763286 by Boreal(15235) $\"\"$ $\"About$

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The 99%CI would be z(0.995)*sigma/sqrt(n), and that has to be < 1.7
\n" ); document.write( "so 2.576*10.1/sqrt(n) <1.7
\n" ); document.write( "square both sides
\n" ); document.write( "676.916/n < 2.89
\n" ); document.write( "so 676.916/2.89\n" ); document.write( "or n > 676.916/2.89
\n" ); document.write( "n>234.22 or 235 \n" ); document.write( "

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