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# Apr. 22 - PowerPoint PPT Presentation

##### Apr. 22

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1. Apr. 22 Stat 100

2. Final Wednesday April 24 • About 40 or so multiple choice questions • Comprehensive • Study the midterms • Copies and answers are at the course web site

3. Exam 4 , White 5 Yellow 17 • 5. In an observational study, confounding means • B. That the effect of the explanatory variable on the response variable changes for different categories of a third variable. • D. That the effect of the explanatory variable on the response variable can't be separated from the effect of other variables on the response.

4. Exam 4, White 13 Yellow 1 13. Eighty individuals who wished to lose weight were randomly divided into two groups of 40. One group was given an exercise program to follow while the other group was given a special diet. After three months, the researcher compared mean weight losses in the two groups. What type of study is this? D. Randomized experiment

5. Exam 4, White 23 Yellow 23 23. Twenty students each are asked to randomly pick either the letter S or the letter Q. Fifteen of the students picked S. The null hypothesis is that the picking is random which means both letters had an equal chance to be picked. Which choice describes a P‑value for testing the significance of the observed data? B. The probability that 15 or more students would pick S if picking is random

6. Exam 4, White 27 Yellow 14 • 27. Which of the following time series is most likely to show a seasonal component if it were graphed? • A. annual sales of gardening tools in the United States • D. monthly highway travel in Pennsylvania

7. Exam 4, White 28 Yellow 3 28. At the end of a newspaper article about a new medication for the relief of cold and flu symptoms, the researcher is quoted as saying that there was a 1 in 3 probability that the observed difference between the medication and a placebo could have occurred due to chance luck. In statistical terms, the researcher is saying the difference between the medication and the placebo was ____. B. not significant

8. Exam 4, White 30 Yellow 19 • 30. An experiment is usually preferred to an observational study because ___. • A It is easier to collect data from an experiment than it is from an observational study. • C. One can draw a cause and effect conclusion in an experiment but not in an observational study.

9. From Exam 3 • 5. A small college wants to know what percentage of its current 1,600 students wants a switch to a quarter system. Every student in the college is polled with a question that's attached to the course registration form. What's the margin of error for the poll? • A. 0% B. 2.5% C. 5%

10. From Exam 3 • 6. Which of the following is the principal benefit of increasing the sample size of a survey? • A. A larger sample size decreases the biasB. A large sample size decreases the margin of errorC. A large sample size improves the statistical validityD. All of choices A,B, and C are true

11. From Exam 2 10. The relative risk of an automobile accident when driving on a Friday night is 50 for drivers who drink and drive. Suppose the risk of an accident for those who don’t drink and drive 2/5000. For those who drink and drive, what is the risk of an accident on a Friday night.?A. 1/250000 B. 100/5000C. 52/5000 D. 50/5000

12. From Exam 2 19. Suppose an equation has been developed that relates college GPA to verbal SAT? What statistical technique has been used? A. Regression B. Chi-square C. Correlation D. Expected Value

13. From Exam 2 • Questions 21 and 22. Suppose the risk of high blood pressure is 15% for smokers and 10% for non-smokers. • 21. What=s the percent increase in risk of high blood pressure for smokers compared to non-smokers? • B. 50% • 22. For non-smokers, what are the odds of having high blood pressure? • C. 1 to 9

14. From Exam 2 29. Molly and Amy each randomly and independently pick a number between 1 and 10. Assume for each, that all numbers are equally likely. What is the probability that they both pick the same number? A. (1)(1/10) B. (1/10)+(1/10) C. (1/10)(1/10) D. 0

15. From Exam 1 • 17. An investigator is doing an observational study to determine whether baldness is an indicator of heart disease in men. He measure the baldness pattern of 200 men with heart disease and also does this for 200 other men without heart disease He selected these other men so that they were about the same age as the heart disease patients. What type of study design is this? • A. Case Control B. Randomized C. Double Blind D. Blocked Experiment

16. From Exam 1 15. A list of four test scores is 80, 60, 100, 70. What is the median score? A. 77.5 B. 60 C. 80 D. 75

17. From Exam 1 • 26. Eighty individuals who wished to lose weight were randomly divided into two groups of forty. Researchers give one group an exercise program to follow, while the other group is given a special diet. What type of study is this? • . Observational B. Case control C. Matched pairs study D. Randomized experiment

18. From Exam 1 31. What is the benefit of using randomization in an experiment? A. the placebo effect is eliminated B. the Hawthorne effect is eliminated C. It guarantees ecological validity D. the risk of confounding is reduced