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renielle renielle
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Use the following to answer the questions below:

"Black Friday," which occurs annually the day after Thanksgiving, is one of the biggest shopping days of the year. During the holiday season, many stores created controversy by starting their mega-sales on Thanksgiving itself. In a random sample of 25 individuals who shopped during the Black Friday four-day weekend (Thursday - Sunday), the average amount spent was $399.40 with standard deviation $171.10. The data are displayed in the provided dotplot.

A dotplot depicts the results of the amount spent during the Black Friday weekend for 25 individuals. The horizontal axis is labeled, Amount spent and has markings from 90 to 720 in increments of 90. The dots are plotted as follows: 1 dot above 70, 130, 140, 210, 250, 260, 270, 300, and 310; 2 dots above 360; and 1 dot above 380, 390, 450, 460, 470, 480, 500, 520, 530, 550, 560, 570, 700, and 750. There are no dots above 90, 180, 630 and 720. All values are approximate.

Suppose we know that in a random sample of n = 22 individuals who shopped over Black Friday weekend in 2011 the average amount spent was $381.30 with standard deviation $119.80. Construct a 95% confidence interval for the difference in the mean amount spent between the 2012 and 2011 Black Friday weekends. Round the margin of error to two decimal places.

Recall that for the 2012 sample of 25 individuals, the average amount spent was $399.40 with standard deviation $171.10. Dotplots of both samples are provided.



▸ -$76.07 to $112.27

▸ -$91.86 to $128.06

▸ -$65.59 to $101.79

▸ -$70.72 to $106.92
Textbook 
Statistics: Unlocking the Power of Data

Statistics: Unlocking the Power of Data


Edition: 3rd
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ecunis1ecunis1
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