Download Statistics Exam: Winter 2002 - Two-Sample t-Test and Confidence Intervals and more Exams Statistics in PDF only on Docsity! Page 1 of 4 St 411/511, D. Schafer, Winter 2002 EXAM This is a 50-minute open-book, open-notes test. Show work where appropriate. (3 points each) Write the letter from the list below that best matches the description. (Let- ters may be used more than once.) 1. __L__ An estimate of the population standard deviation. 2. __G__ The average size of squared deviations of population values from their mean. 3. __C__ A measure of the degree of credibility in a null hypothesis. 4. __J__ A property that a statistical tool is said to have if it is insensitive to outliers. 5. __H _ The distribution of values of a statistic over all possible random allocations. 6. __H__ The name of the permutation distribution when applied to a randomized experiment. 7. __Q__ An estimate minus the parameter it estimates, divided by its standard error. 8. __Q__ A quantity that is the same as the t-statistic if the null hypothesis is true. 9. __I__ A method for finding a p-value that is directly related to the chance involved in random allocation of subjects to treatment groups. 10.__N__ The estimated typical size of a deviation of an estimate from the parameter it estimates. A. 95% confidence interval H. randomization distribution O. standard normal distribution B. confounding variable I. randomization test P. t distribution C. p-value J. resistance Q. t-ratio D. permutation distribution K. robustness R. t-statistic E. population distribution L. sample standard deviation S. two-sample t-test F. population standard deviation M. sampling distribution T. variability G. population variance N. standard error U. z-statistic Your name:______________________________________ Your lab time (Circle one): 8:00 10:00 12:00 Page 2 of 4 11. (3 points). Summary statistics are shown below for vertical jumping heights (change in center of gravity, in cm) for 7 volleyball players from the Finnish national team and 11 volleyball play- ers from the Russian national team. Finns n1 = 7 Y1 = 46 s1 = 3.2 Russians n1 = 11 Y2 = 50.75 s2 = 6.4 What is the pooled estimate of standard deviation? (Show work.) 12. (3 points) How many degrees of freedom are associated with the two-sample t-test for com- paring the two groups in problem 11. 16 13. (3 points) Is the study in problem 11 a randomized experiment or an observational study? _____ Randomized experiment ___X_Observational study 14. (3 points) Calculate the rank-sum statistic from the following two groups of numbers. Show work. Circle your answer. group 1: 1, 7, 19 group 2: 1, 5, 3 Values: 1 1 3 5 7 19 Group: 1 2 2 2 1 1 Order: 1 2 3 4 5 6 Rank: 1.5 1.5 3 4 5 6 Sum of ranks for Group 1 values: 1.5 + 5 + 6 = 12.5 2 2(7 1)3.2 (11 1)6.4 (7 1) (11 1)p s − + − = − + − 29.44 5.43= =
