17. The four departments of a printing company are listed Administration Sales Production Billing 18. The total compensations (in millions of dollars ) of the top ten CEOs in the United States are listed . (Source : Forbes ) 131 67 64 61 56 50 40 44 43 SECTION 1.3 In Exercises 19 and 20, determine whether the study is an observational study or an experiment . Explain 19. Researchers conduct a study to determine whether a drug used to treat hypothyroidism works better when taken in the morning or when taken at bedtime . To perform the study , 90 patients are given one pill to take in the morning and one pill to take in the evening (one containing the drug and the other a placebo ). After 3 months , patients are instructed to switch the pills . (Source : JAMA Internal Medicine 20. Researchers conduct a study to determine the number of falls women had during pregnancy . To perform the study , researchers contacted 3997 women who had recently given birth and asked them how many times they fell during their pregnancies . (Source : Maternal and Child Health Journal ) In Exercises 21 and 22, two hundred students volunteer r for an experiment to test the effects of sleep deprivation on memory recall . The students will be placed in one of five different treatment groups , including the control group . 21. Explain how you could design an experiment so that it uses a randomized block design . 22. Explain how you could design an experiment so that it uses a completely randomized design . In Exercises 23-28, identify the sampling technique used , and discuss potential sources of bias (if any ). Explain 23. Using random digit dialing, researchers ask 1003 U.S. adults their plans on working during retirement. (Source: Princeton Survey Research Associates International) 24. A student asks 18 friends to participate in a psychology experiment 25. A pregnancy study in Cebu, Philippines, randomly selects 33 communities from the Cebu metropolitan area, then interviews all pregnant women in these communities. (Source: Cebu Longitudinal Health and Nutrition Survey) 26. Law enforcement officials stop and check the driver of every third vehicle for blood alcohol content 27. Twenty -five students are randomly selected from each grade level at a high school and surveyed about their study habits . 28. A journalist interviews 154 people waiting at an airport baggage claim and asks them how safe they feel during air travel . 29. Use the fifth row of Table 1 in Appendix B to generate 8 random n numbers between 1 and 650 30. You want to know the favorite spring break destination among 15,000 students at a university . Determine whether you would take a census or use a sampling . If you would use a sampling , decide what sampling technique you would use . Explain your reasoning