document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=565140>Question 565140</A>: <I><SPAN STYLE=\"word-break: break-all;\"> The lifetime of a certain brand of battery is known to have a standard deviation of 16 hours. Suppose that a random sample of 90 batteries has a mean lifetime of 41.1 hours. Find a 95% confidence interval for the true mean lifetime of all batteries of this brand.  </SPAN>\n" );
document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #365660 by </B><A HREF=/tutors/aboutme.mpl?userid=stanbon><B>stanbon(75887)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=stanbon><IMG SRC=http://www.algebra.com/images/aboutme-small.gif BORDER=0 alt=\"About Me\" VALIGN=MIDDLE></A>&nbsp;<IMG SRC=http://www.algebra.com/images/nopicture.jpg><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=365660\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\">  The lifetime of a certain brand of battery is known to have a standard deviation of 16 hours. Suppose that a random sample of 90 batteries has a mean lifetime of 41.1 hours. Find a 95% confidence interval for the true mean lifetime of all batteries of this brand.<BR>\n" );
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document.write( "sample mean: 41.1<BR>\n" );
document.write( "margin of error: 1.96*(16/sqrt(90)) = 3.3056<BR>\n" );
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document.write( "CI: 41.1 - 3.3056 < u < 41.1 + 3/3056<BR>\n" );
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document.write( "Cheers,<BR>\n" );
document.write( "Stan H.<BR>\n" );
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