document.write( "<A HREF=/cgi-bin/jump-to-question.mpl?question=1200322>Question 1200322</A>: <I><SPAN STYLE=\"word-break: break-all;\"> In a survey, 10 people were asked how much they spent on their child's last birthday gift. The results were roughly bell-shaped with a mean of $36 and standard deviation of $4. Find the margin of error at a 95% confidence level.\r<BR>\n" );
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document.write( "Give your answer to three decimal places. </SPAN>\n" );
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document.write( "Answer: <font color=red size=4>2.479</font>\r<BR>\n" );
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document.write( "Explanation:\r<BR>\n" );
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document.write( "At 95% confidence, the z critical value is roughly z = 1.960<BR>\n" );
document.write( "Use a calculator with built in stats functions (eg: TI84) or a reference table to determine this value.\r<BR>\n" );
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document.write( "Here is one such table<BR>\n" );
document.write( "<a  rel=nofollow HREF= \"https://www.sjsu.edu/faculty/gerstman/StatPrimer/t-table.pdf\">https://www.sjsu.edu/faculty/gerstman/StatPrimer/t-table.pdf</a><BR>\n" );
document.write( "Scroll to the bottom to locate 1.960, which is one cell above the \"95% confidence level\".\r<BR>\n" );
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document.write( "The margin of error formula for the mean is<BR>\n" );
document.write( "E = z*sigma/sqrt(n)<BR>\n" );
document.write( "where,<ul><li>z = critical value mentioned earlier = 1.960</li><li>sigma = standard deviation = 4</li><li>n = sample size = 10</li></ul>Take note that the mean isn't involved with the margin of error formula.\r<BR>\n" );
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document.write( "So,<BR>\n" );
document.write( "E = z*sigma/sqrt(n)<BR>\n" );
document.write( "E = 1.960*4/sqrt(10)<BR>\n" );
document.write( "E = 2.479225685572<BR>\n" );
document.write( "E = <font color=red>2.479</font><BR>\n" );
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