problemset9solution - 1 PAM 210 Lecture 1 Problem Set #9...

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PAM 210 Lecture 1 Problem Set #9 Posted: 14 th April, 2008 Due date: 21 st April, 2008 #1) 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. Ans. The t-statistic is 338 . 2 31 / 10 0 2 . 4 - = t (10 points . Full credit for the correct answer. 8 points if the final answer was wrong but the formula was correct) b) Is the result statistically significant at the 1% level? Ans. The df =31-1=30. Since this is a two-sided test, the critical value is 75 . 2 ) 30 ( 005 . 0 = t . Since 2.338<2.75, the result is not significant at the 1% level. (10 points. Full credit if the final answer is correct (significant/not significant). If the final answer is wrong, then 5 points for correct df, and 3 more points for the correct critical value) #2) A bank wonders whether omitting the annual credit card fee for customers who charge at least three thousand dollars in a year would increase the amount charged on its credit card. The bank makes this offer to an SRS of 1001 of its existing credit card customers. It then compares how much these customers charge this year with the amount
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problemset9solution - 1 PAM 210 Lecture 1 Problem Set #9...

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