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HW_9_S10[1]

# HW_9_S10[1] - AEM 2100 Spring 2010 Homework 9 1 Name...

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AEM 2100 Name: _________________ Spring 2010 Section:_________________ Homework 9 1.) A sample of 20 pages was taken without replacement from the 1,591-page phone directory Ameritech Pages Plus Yellow Pages . On each page, the area devoted to display ads was measured (a display ad is a large block of multicolored illustrations, maps, and text). The data (in square millimeters) are shown below: 0 260 356 403 536 0 268 369 428 536 268 396 469 536 162 338 403 536 536 130 a.) Construct a 95% confidence interval for the true mean. b.) Construct a stem and leaf plot. Why might the normality assumption be an issue here? c.) What sample size would be needed to obtain an error of + 10 square millimeters with 99 percent confidence? (You can use the previous data to obtain a variance estimate.) d.) If your answer from part c does not give a reasonable sample size, suggest a way to address this problem. If it does, leave this question blank. 2.) When do Americans decide what to make for dinner? An online survey (extracted from N. Hellmich, “Americans Go for the Quick Fix for Dinner,” USA Today , February 14, 2005, p. 1B) indicated that 74% of Americans decided at the last minute. Suppose that the survey was based on 500 respondents. a.) Construct a 95% confidence interval estimate for the proportion of Americans who decided what to make for dinner at the last minute. b.) Construct a 99% confidence interval estimate for the proportion of Americans who decided what to make for dinner at the last minute. c.) Which confidence interval is wider? Explain why this is true?

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3.) Hoping to lure more shoppers downtown, a city builds a new public parking garage in the central business district. The city plans to pay for the structure through parking fees. During 22 weekdays, daily fees collected averaged \$1,264 with a standard deviation of \$150. a.)
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HW_9_S10[1] - AEM 2100 Spring 2010 Homework 9 1 Name...

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