Week 1 E-Text

# Week 1 E-Text - 8.48 A sample of 20 pages was taken without...

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8.48 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 mean 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 percent confidence interval for the true mean. (b) Why might normality be an issue here? (c) What sample size would be needed to obtain an error of ±10 square millimeters with 99 percent confidence? (d) If this is not a reasonable requirement, suggest one that is. (Data are from a project by MBA student Daniel R. Dalach.) A) Sample mean 346.5 Standard deviation = 170.3784 Standard error of mean = sd / sqrt(n) SE = 170.3784/4.4721 Standard error of mean 38.0978 Confidence limits 346.5-(38.0978)(2.093) and 346.5+(38.0978)(2.093) 95 % limits for mean is (266.7614, 426.2386) B) Normality might be an issue because of the small sample size. C)

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## This note was uploaded on 12/19/2010 for the course MKT 521 taught by Professor Vitale during the Spring '10 term at University of Phoenix.

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Week 1 E-Text - 8.48 A sample of 20 pages was taken without...

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