Practice Final A WI 2011

# A true b false 25 if the normal probability plot

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a. True b. False 25. If the normal probability plot shows a straight line through (0,0) with slope 1, then: a. The data have a linear relationship. b. The data has a normal distribution. c. None of the above. 26. Suppose you have two scatterplots; the first one has points lining up perfectly, going uphill with a slope of 10. The second scatterplot has points lining up perfectly going uphill with a slope of 1/10. Which scatterplot has a higher correlation? 27. Suppose you want to determine the percentage of students in our class who are looking for an internship for next year. Taking a stratified random sample of 50 men and 50 women and finding the overall percentage looking for an internship would be a good sampling plan. a. YES b. NO 28. Which situation gives you less bias? 29. Let X = the number of coin flips you need to get a tail. X has a binomial distribution. 30. I took a random sample of size n and got a mean 80 and standard deviation 10. I used it to find a confidence interval for the population mean, and my margin of error was 1. What size sample did I take? a. 384 b. 384.16 c. 385 6

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d. None of the above RECORD YOUR ANSWERS TO ALL ABOVE Q’s ON THE ANSWER SHEET ON THE LAST PAGE. WE WILL ONLY GRADE WHAT IS ON THE ANSWER SHEET FOR THESE PBMS 7
SHOW YOUR WORK PROBLEMS: 7 PBMS, 10 PONTS EACH NO WORK = NO CREDIT – THIS GOES FOR ALL PROBLEMS ! ASSUME ALL CONFIDENCE INTERVALS ARE 95% IF YOU NEED CLT, YOU MUST TELL US WHY! CHECK ALL CONDITIONS! For #31-33: Suppose test scores on an accounting exam have a normal distribution with mean 80 and standard deviation 8. 31. You select one student at random. What is the chance their score is more than 83? ANS______________ 32. What exam score is at the 80 th percentile? ANS______________ 33. Select 49 students at random. What’s the chance the average score is more than 83? ANS_______________ For #34: Quiz scores (10 points each) for two quizzes are analyzed for 6 students. The regression analysis is below. What is the residual for the point where X = 4? Use proper units and show all work for credit. DATA: ANALYSIS: Quiz 1 Quiz 2 Predictor Coef SE Coef T P 5 5 Constant 1.533 2.431 -0.63 0.562 2 3 Quiz 1 0.9429 0.6242 -1.51 0.205 3 3 S = 2.61133 R-Sq = 36.3% R-Sq(adj) = 20.4% 4 10 6 6 1 2 ANS___________ 8

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For #35-36: Bob heard on the news that 30% of all employees would prefer to work from home one day a week. SHOW WORK!
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