3. What's the correct set of expected counts for a Chi-Square test of the relationship?

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1 STAT 200 EXAM 1 SPRING 2000 Questions 1-4. A recent study found that college students who habitually procrastinate are more likely to get colds. Three hundred college students are asked how often they procrastinate and if they=ve had a cold in the last two months. The data are then categorized into the following contingency table of counts: Had a Cold? Yes No Total Often Procrastinate Rarely Procrastinate Among people who often procrastinate, what's the risk of having a cold in the last two months? A B C D What=s the relative risk of having had a cold for people who often procrastinate compared to those who rarely procrastinate? A. 1.0 B. 2.0 C. 4.0 D. None of choices A,B, or C are correct. 3. What's the correct set of expected counts for a Chi-Square test of the relationship? A. Yes. No B. Yes. No C. Yes. No Often Often Often Rarely Rarely Rarely Which of the following would we learn from calculating the row percents for these data? A. Of those who had a cold, what percent often procrastinates? B. Of those who often procrastinate, what percent had a cold? C. What percent of all 300 has both had a cold and also rarely procrastinates? 5. The relative risk of allergies for children of parents who smoke compared to children of parents who do not smoke is 3.0. Suppose that the risk of allergies for the children of non-smokers is 6%. What is the risk of allergies for the children of smokers? A. 12% B. 18% C. 2% D. 50% 6. Which of the following examples is an example of Simpson s Paradox? A. In a sample the percentage of men with a tattoo is higher than the percentage of women with a tattoo. But, a chi-square test indicates there may not be a statistically significant relationship. B. There is an observed association between daily exercise habits and blood pressure, but this may occur because people who exercise more also have better diets. C. Over a whole university, the percentage of applicants admitted was higher for men than for women. Yet, within every major, the percentage admitted was actually higher for women than it was for men. D. All of choices A, B, and C are examples of Simpson s Paradox. 7. The probability that it snows tomorrow is ¼ = 25% and the probability that it does not snow tomorrow is ¾ =75%. What are the odds that it will snow tomorrow? A. 4.0 B. 3 to 4 C. 1 to 3 D. 1 to 4

2 Page 2 Omitted The relationship between gender and willingness to help somebody who has dropped some pencils is examined using a Chi-square test. The p-value for the Chi-square test is found to be What is the most appropriate conclusion? A. There is a statistically significantly relationship between gender and willingness to help because the p- value is less than B. There is a not a statistically significant relationship between gender and willingness to help because the p-value is higher than C. We can t say whether there is a statistically significant relationship because we don t know the sample size. Questions 8 to 10 refer to the following stem and leaf plot of the pulse rates of 18 college students. The pulse rates range from 58 to What is the median pulse rate for these 18 students? A. 70 B. 72 C. 73 D What pulse rate is the lower quartile for these 18 students? A. 66 B. 67 C. 68 D Suppose that it s discovered that a mistake was made when the highest pulse rate was recorded and that this pulse is actually 86 (not 92). Which of the following statistics would be affected by this mistake? A. median B. standard deviation C. lower quartile D. IQR 11. Which one of the following choices does NOT measure the variation among measurements? (Only one answer is right.) A. IQR B. standard deviation C. Median D. range 12. The mean systolic blood pressure of adult women is 120 and the standard deviation is 10. Use the empirical rule to complete the following sentence. About 99.7% of all adult women have a blood pressure between. A. 110 and 130 B. 100 and 140 C. 90 and 150 D. 30 and True or False? The mean and the median of a list of data are always equal to each other. A. True B. False

3 Page A medical doctor is comparing two treatments for high cholesterol. She has 40 patients available to participate in a clinical trial. She puts the names of the 40 people into a box and randomly draws the names of 20 people who will be assigned to treatment A. The other 20 individuals will be assigned to treatment B. What type of study design is this? A. randomized experiment B.sample survey C. observational study D. confounded Question A research project done to see how the use of oral contraceptives affected the blood pressures of women. One problem with the research was that the women who used oral contraceptives were younger than the other women were. 15. What type of study design was used in this example? A. blocked B. Experiment C. Observational D. Double Blind 16. In this study, what is the best term to use for the variable blood pressure? A. confounding variable B. blocked C. explanatory variable D. response variable 17. In this study, what is the best term to use for the variable age? A. confounding variable B. response variable C. explanatory variable D. outcome variable 18. In a class survey, a question was Do you have a tattoo? Which of the following graphs is best for comparing the percent of women with a tattoo to the percent of men with a tattoo? A. stemplot B. dotplot C. boxplot D. bar graph 19. Suppose that an investigator uses randomization to assign the participants in an experiment to two different treatment groups. What is the benefit of doing this? (Only one answer is right.) A. It eliminates the Hawthorne effect B. It eliminates the placebo effect C. It improves the ecological validity of the experiment. D. It reduces the risk that confounding will affect the results. 20. In a small graduate math class with only five students, the professor gives an easy exam. Four of the scores are higher than 90, but the class goof-off gets a 30. Which of the following is true? A. The median and mean scores are the same. B. The mean score is greater than the median score C. The mean score is less than the median score 21. A list of eight scores on a test is 80, 56, 94, 68, 76, 82, 90, 98. Which of the following choices is the upper quartile? A. 82 B. 86 C. 90 D. 92

4 Page In a survey, four hundred students are asked what type of growth they feel is more important in college- intellectual or social. Which of the following statistics would be an appropriate summary of the data? A. percent who respond intellectual B. the mean C. the median D. all of choices A through C would be appropriate summaries here. Questions 23 and 24 refer to this information The self-reported heights of college men have a mean of 71 inches and a standard deviation of 3 inches. 23. What height is two standard deviations taller than the mean? A. 6 B. 73 C. 77 D Use the empirical rule to complete the next sentence. About 95% of college men have a selfreported height between. A. 68 and 74 B. 65 and 77 C. 62 and 80 D. 71 and 84. Questions 25 to 28 refer to the following five number summaries of the forearm lengths (in centimeters) of college men. Men Median 26 Quartiles Extremes The interquartile range is. A. 2 cm B. 3 cm C. 12 cm D. Impossible to determine 26. The shortest ¼ of the forearm lengths are less than. A. 38 B. 28 C. 26 D About ¼ of the men have a forearm length longer than A. 25 B. 26 C. 28 D The maximum measurement is 36 cm. Which of the following statements is the most correct about this measurement? A. This measurement is an outlier because the most extreme point is always called an outlier. B. This point is not an outlier because it s not sufficiently far from the upper quartile to be labeled as an outlier. C. This point is an outlier because nobody could have a forearm that long. D. This point is an outlier because it is far enough away from the upper quartile to be called an outlier.

5 Page What does the phrase "Hawthorne effect" mean? A. A placebo has been used in the experiment. B. A placebo is often effective. C. A treatment is often more effective in an experiment than in real life D. The experiment was randomized. 30. An investigator is doing an observational study to compare the incidence of lung disease in asbestos plant workers to the incidence of lung disease in other workers. He selects the other workers so that they have the same smoking habits as the asbestos workers. What type of study design is this? A. Simple random sample B. Randomized C. Double Blind D. Case Control Questions In each of the following situations, indicate whether the raw data would constitute a categorical variable, a quantitative variable of an ordinal variable. 31. Responses to the question Do you favor or oppose the death penalty for persons convicted of murder? 32. Responses to the question What is your height? 33. Responses to the question About how many classes do you skip in a semester? 34. Responses to On a scale of 0 to 100 (where 100=the best), rate how much you like Latin music Which of the following statements follows from the Fundamental rule for using data for inference? A. The only data that can be ever used for inference are the data from a simple random sample. B. The only data that can be ever used for inference are the data from a randomized experiment. C. A convenience sample (like the members of our class) can never be used for inference. D. None of statements A, B, or C follow from the Fundamental rule for using data for inference. 36. A college newspaper does a survey of students who live on campus. It does this by randomly sampling 5 students from each dormitory on campus. Which statement is true? A. The newspaper s sample is a simple random sample. B. The newspaper s sample is not a simple random sample.

6 Page 6 Questions 37,38, and 39 refer to the following histogram of the number of CDs owned by a sample of college students. 37. Which of the following terms describes the shape of the histogram? A. symmetric but not bell-shaped B. bell-shaped C. skewed D. confounded 38. Which of the following choices is closest to being the median of the data? A. 50 B. 100 C. 125 D Which statistic will be a larger number? A. median B. mean *****************END OF EXAM ***********************************