problemset7solution - PAM 2100 Spring 2009 Problem Set #7...

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PAM 2100 Spring 2009 Problem Set #7 Answer Key Total points: 10 #1) from the textbook: 7.38 Use df=1000. Round your final answer to four decimal places. (2 points) (The actual degree of freedom of this problem is 1406-1=1405. But since we do not have the t-values for this df in table D, we will use df=1000.) The value of t , for df=1000 and confidence level 99%, is 2.581. So the confidence interval is 0675 . 9 . 3 1406 98 . 0 * 581 . 2 9 . 3 ± = ± = ± = m x ( 1 point for the correct value of t , 1 point for the correct margin of error) (if someone uses n=1000 or 1001 by mistake, but the methods are otherwise correct, then take only 1 point off) #2) You will have complete sales information for last month in a week, but right now you have data from a random sample of 31 stores. The mean change in sales in the sample is x = 4.2 and the standard deviation of the changes in the sample is s = 10. Here are the null and alternative hypotheses: H 0 : μ = 0 H a : μ 0 a) Find the t-statistic. Round your answer to three decimal places, if necessary.
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problemset7solution - PAM 2100 Spring 2009 Problem Set #7...

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