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1 SOC 360 Practice Exam 2 Answer Key Part I True/false 1. False 2. False 3. True 4. True 5. True 6. False Part II. Multiple Choice 7. B 13. A 8. D 14. E 9. A 15. A 10. C 16. A 11. G 12. B Part III. 17. SD = 100/ 20 = 22.36 B. normal distribution. C. P( x > 560) = P(Z > (560-500)/22.36) = P(Z > 2.68) = 1-0.9963 = 0.0037 18. A. Let X be the annual return of stocks, P(X < 0) = P(Z < (0-10)/26) = P(Z < -0.385) = 0.3483 (0.3520 is OK too) B. SD = 26 / 45 = 3.88 (%) C. P(X < 0) = P(Z < (0-10)/3.88) = P(Z < -2.58) = 0.0049 D. The probability of a loss in the long term is much smaller than that in the short term (0.0049 vs. 0.3483) 19A. z* = 1.645 19B. z* = 2.807 20A. SD = 2000 / 325 = 110.94 20B. a 98% CI: 6200 ± 2.326*(110.94) = 6200 ± 258.05 = (5942, 6458) 20C. ± 258 (258 OK) 21A. x = 107.8, a 96% CI: 107.8 ± 2.054* (15/ 10 ) = 107.8 ± 9.74 = (98.06, 117.54) 21B. No, we cannot reject H0 because 100 is within the 96% CI. There is no significant evidence that mean IQ scores in the population differs from 100 at α = 0.04 level. 2 22A SD = 35/ 25 = 7 22B Note: the center of density curve is 120, 95% of area is between 106 and 134. (shape: normal; mean = 120; pay attention to the width when you draw the curve.) 22C The test is two-tailed, so the area to the right of 130 and to the left of 110 is shaded. 23A H0: µ = 7.5 Ha: µ < 7.5 7 − 7 .5 23B. z = = -1.414 2.5 / 50 23C. (z < -1.414) = 0.0793 23D. cannot reject H0. 24A. H0: µ = 12 Ha: µ ≠ 12 12.9 − 12 24B. z = =3 3 / 100 24C. P(z >3) = 1-0.9987 = 0.0013, p-value = 2* 0.0013 = 0.0026 24D. Reject H0, very good evidence against the politician’s claim. 25A. a 95% CI: 8.6 ± 1.96*( 3 .2 ) = 8.6 ± 0.3626 = (8.24, 8.96) 300 25B. n = (1.96*3.2/0.1)2 = 3933.8, we take n = 3934 26A. All faculty of Occidental University 26B. Stratified Random Sampling 26C. Undercoverage. 27. Larger sample size for women than men.