document.write( "Question 808112: You wish to estimate µ, the average
\n" ); document.write( "lifetime of a particular type of battery. You are
\n" ); document.write( "planning to select n batteries of this type and to
\n" ); document.write( "operate them continuously until they fail. You
\n" ); document.write( "have some feeling that the standard deviation of
\n" ); document.write( "the lifetimes should be around 20 hours, and you
\n" ); document.write( "wish your estimate of µ to be within 1 hour of
\n" ); document.write( "µ with 95% confidence. How many batteries
\n" ); document.write( "should you select?
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Algebra.Com's Answer #486743 by stanbon(75887)\"\" \"About 
You can put this solution on YOUR website!
You are
\n" ); document.write( "planning to select n batteries of this type and to
\n" ); document.write( "operate them continuously until they fail. You
\n" ); document.write( "have some feeling that the standard deviation of
\n" ); document.write( "the lifetimes should be around 20 hours, and you
\n" ); document.write( "wish your estimate of µ to be within 1 hour of
\n" ); document.write( "µ with 95% confidence. How many batteries
\n" ); document.write( "should you select?
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\n" ); document.write( "n = [z*s/E]^2
\n" ); document.write( "----
\n" ); document.write( "n =[1.96*20/1]^2 = 39.2^2 = 1567 when rounded up
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\n" ); document.write( "Cheers,
\n" ); document.write( "Stan H.
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