1 Spring 2013 STAT 110 Exam 2 Practice sum of observationsn  =  − 2 A study at Yale Medical School investigated treatments for chronic cocaine abusers who wanted to quit. It was thought that males and females might respond differently to treatment. There were 72 male and 30 female subjects. Males were randomly assigned to one of three treatments: desipramine, lithium, or a pill with only inert ingredients. Each woman was also assigned randomly to one of these three treatments. Neither the subjects nor their physicians knew which treatment they were receiving. After six weeks, the subjects verbally reported their cocaine use status (degree of use during the six week period). Results were reported separately for males and females. 1. An example of an ethics violation would be A) not using informed consent B) not gaining permission for the study from the Yale Institutional Review Board C) reporting summary results in a journal article D) allowing an individual’s results to lie open in public view E) (A), (B), and (D) 2. The Yale Institutional Review Board for this study would A) only determine whether the study is well designed and hence will yield valuable information B) only determine whether the study is statistically sound C) only review the study to protect the rights and welfare of human subjects D) not be necessary 3. Notice this study used the verbal answer from each subject to measure the cocaine use status after six weeks of treatment. It has been argued that verbal reporting of cocaine use will cause subjects to lie (and say they used less than they really did) and this will create an underestimate of cocaine use status. If everyone under reported their cocaine use status, this would make the researcher’s estimate of cocaine use status a(n)__________________ estimate. A) biased B) reliable C) unreliable D) valid 4. Suppose the researchers decided to test a sample of the patient’s hair for evidence of cocaine use over the last six weeks (instead of using verbal reporting). The machine that does the testing on a strand of hair is the A) instrument B) measurement C) variable D) unit of measure 5. Using the average of six measurements on the hair for each patient instead of a single measurement, would make this measurement more A) biased B) unbiased C) reliable D) unreliable 6. There were 18 million homes with cable TV access in 1980 and there were 73 million homes in 2005. Find the percent increase in the number of homes with cable TV. A) = 0.75 ⇒ 75% B) = 3.06 ⇒ 100% C) = 3.06 ⇒ 306% 7. A manufacturer of a new synthetic oil claims that its oil can reduce car maintenance costs by 150%. This means that A) car owners using the synthetic oil will pay 150% less B) car owners not using the synthetic oil will pay 150% more C) car owners using synthetic oil will pay 100% less D) it does not make sense to talk about reducing costs by 150%3 8. In the class poll, you were asked for your class (freshman, sophomore, junior, or senior). What type of variable is “class”? a. Categorical: Nominal b. Categorical: Ordinal c. Quantitative: Continuous d. Quantitative: Discrete 9. Suppose we measure the mass of a textbook (in kilograms) used in a class. What type of variable is “textbook mass”? a. Categorical: Nominal b. Categorical: Ordinal c. Quantitative: Continuous d. Quantitative: Discrete 10. You have data on the average SAT score of entering University students for several universities. Which of the following is the best graphical display if you want to compare average SAT score across the different universities? a. Pie Chart b. Bar Chart c. Line Graph d. Histogram 11. The following are data on numbers of rats per week spotted in LeConte for 6 weeks. 3 10 10 6 2 5 Find the median number of rats. a. 5.5 rats b. 6 rats c. 10 rats d. 36 rats 12. The following are data on numbers of rats per week spotted in LeConte for 6 weeks. 3 10 10 6 2 5 Find the mode for number of rats. a. 5.5 rats b. 6 rats c. 10 rats d. 36 rats If you want more practice, compute the mean for the rat data – answer on the solution guide!4 The following graphical display shows typical age at first marriage. 13. What type of graphical display is this? a. Pie Chart b. Bar Chart (side by side) c. Line Graph d. Histogram 14. Which statement is correct? a. college education status explains age at first marriage completely b. college education status does not explain age at first marriage at all c. age at first marriage is tending to increase over time for both groups d. age at first marriage is staying the same over time for both groups 15. What other type of graphical display would have worked nicely to show how the age at first marriage changes over these years? a. 2 Pie Charts (college and non-college educated) b. Line Graph (with 2 lines - one for each group) c. 2 Histograms (college and non-college educated) Consider the following boxplot of some exam scores: 16. What percent of exam scores are between 71.5 and 92.5? a. 25% b. 50% c. 75% d. 100% 17. What is the Q1, that is the first quartile of the exam score distribution? a. 71.5 b. 84.5 c. 92.5 d. Cannot be determined5 The following plot depicts the exam scores for 500 students. 18. The shape of the distribution of scores is a. Symmetric b. Skewed right c. Skewed left d. Not enough data to tell 19. For the exam score distribution, we would report as a measure of center and spread a. The mean and standard deviation b. The median and quartiles c. The mode and outliers d. Not enough data to tell 20. Refer to the Exam Score Distribution graphical display. This is an example of a a. Frequency bar chart b. Relative frequency bar chart c. Frequency histogram d. Relative frequency histogram 21. Refer to the Exam Score Distribution graphical display. Which is true? a. Mean < median b. Mean > median c. Mean ≠ median d. Can’t determine relationship between mean and median without doing a calculation 22. Refer to the Exam Score Distribution graphical display. Approximately how many students had a score of an 80? a. About 95 b. About 5 c. Can’t get that