document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1065438>Question 1065438</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In order to estimate the mean amount of time computer users spend on the internet each&#8203; month, how many computer users must be surveyed in order to be 90&#8203;% <BR>\n" );
document.write( "confident that your sample mean is within 15 minutes of the population&#8203; mean? Assume that the standard deviation of the population of monthly time spent on the internet is 195 min. What is a major obstacle to getting a good estimate of the population&#8203; mean? Use technology to find the estimated minimum required sample size.\r<BR>\n" );
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document.write( "The minimum sample size required is computer users.(Round up to the nearest whole&#8203; number.)\r<BR>\n" );
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document.write( "What is a major obstacle to getting a good estimate of the population&#8203; mean?\r<BR>\n" );
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document.write( "A.It is difficult to precisely measure the amount of time spent on the&#8203; internet, invalidating some data values.\r<BR>\n" );
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document.write( "B.The data does not provide information on what the computer users did while on the internet.\r<BR>\n" );
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document.write( "C.There may not be 458 computer users to survey.\r<BR>\n" );
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document.write( "D.There are no obstacles to getting a good esitmate of the population mean.<BR>\n" );
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document.write( "</I><HR><TABLE width=100%><TR><TD><B><A HREF=http://www.algebra.com/>Algebra.Com's</A> Answer #680723 by </B><A HREF=/tutors/aboutme.mpl?userid=rothauserc><B>rothauserc(4718)</B></A><img src=\"/images/stars/stars-13.gif\" alt=\"\" >&nbsp;<A HREF=/tutors/aboutme.mpl?userid=rothauserc><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/cgi-bin/show-face.mpl?user=rothauserc><BR>You can <A HREF=\"/cgi-bin/embed-solution.mpl?show=1&solution=680723\">put this solution on YOUR website!</A><BR><SPAN STYLE=\"word-break: break-all;\"> we use the following formula for margin of error(ME)<BR>\n" );
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document.write( "ME = z * s / square root(n) where z is the z-score we use to calculate the confidence interval, s is the standard deviation, n is sample size and ME is the desired margin of error<BR>\n" );
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document.write( "we want a 90% confidence interval(CI)<BR>\n" );
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document.write( "alpha(a) = 1 - (90/100) = 0.10<BR>\n" );
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document.write( "critical probability(p*) = 1 - (a/2) = 0.95<BR>\n" );
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document.write( "z-score associated with p* is 1.644853<BR>\n" );
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document.write( "15 = (1.644853) * 195) / square root(n)<BR>\n" );
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document.write( "square root(n) = 320.746335 / 15<BR>\n" );
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document.write( "n =  457.2365 approximately 457<BR>\n" );
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document.write( "answer is C<BR>\n" );
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