Question

1. In the regression equation, the value that gives the amount by which Y changes for one unit in X is called the (a) coefficient of correlation. (b) coefficient of determination. (c) slope. (d) intercept.

2. For any two categorical variables, X and Y, the best way to determine if they are related is to (a) calculate the correlation between X and Y. (b) draw a scatterplot of the X and Y values. (c) make a two-way table of the X and Y values. (d) All of the above.

3. The letter grades given in a course are one of A, B, C, D, or F. This grading scale is an example of (a) a nominal scale. (b) an ordinal scale. (c) a response scale. (d) an interval or ratio scale.

4. Suppose a straight line is fit to data having response variable y and explanatory variable x. Predicting values of y for values of x outside the range of the observed data is called contingency. causation. correlation. extrapolation.

5. You compute the correlation coefficient between hours of TV watched each week and gradepoint index for a group of college students, and you obtain r = - 1.65. This means that (a) you made an arithmetic mistake. (b) students who watch more TV tend to get lower grades. (c) students who watch more TV tend to get higher grades. (d) there is little association between TV viewing and gradepoint index.

6. A set of data is found to have a sample standard deviation of 25. Suppose 9 were added to each of the numbers in the data. The standard deviation of the resulting data (a)would now be 34. (b)would still be 25. (c)would now be 28. (d)cannot be determined.

7. Are patches more effective than oral medication in helping individuals stop smoking? Two researchers had 22 people who were randomly assigned to one of the two treatment groups, with 11 people assigned to each. The subjects were monitored for six weeks, during which they received treatment every day—a new patch for subjects in the first group and a single pill for subjects in the second group. The researchers reported that subjects wearing the patches were less likely to quit smoking, although the difference was not statistically significant. This study is a(n) (a) convenience sample. (b) observational study. (c) experiment, but not a double-blind experiment. (d) double-blind experiment.

8. The Physicians' Health Study followed 22,000 male physicians for a period of several years. About 11,000 took an aspirin every second day, while the rest took a placebo. At the completion of the study, it was noted whether a subject had experienced a heart attack during the period of the study. It was found that the aspirin group had significantly fewer heart attacks than the placebo group. The response variable in this experiment is (a) whether a heart attack occurred. (b) the placebo effect. (c) whether the symptoms lessened. (d) the length of the interview.

9. A study of the salaries of full professors at Upper Wabash Tech shows that the median salary for female professors is considerably less than the median male salary. Further investigation shows that the median salaries for male and female full professors are about the same in every department (English, physics, etc.) of the university. This apparent contradiction is an example of (a) extrapolation. (b) Simpson’s paradox. (c) causation. (d) correlation.

10. A distribution of home prices is skewed to the right. Consider the following statements concerning this distribution: (i) the mean is larger than the median. (ii) half the area of the histogram of the distribution falls to the left of the median. (iii) the variable is on the ratio scale of measurement. Which of the above statements are true? (a) only (i). (b) only (ii). (c) only (i) and (ii) (d) only (ii) and (iii) (e) all of them.

11. During the first week of August, 25 women and 15 men joined a weight control club. The average age of the women was 32 and the average age of the men was 28. What was the average age for the entire group? (a) 29.5 (b) 30 (c) 30.5 (d) 31 (e) none of the above

12. Consider the following statements concerning a box plot: (i) it can be constructed from data on a nominal scale. (ii) it can be used to identify skewness in the data. (iii) it can be used to identify outliers. Which of the above statements are true? (a) only (i). (b) only (ii). (c) only (i) and (ii) (d) only (ii) and (iii) (e) none of them.

Answer 1

1. a)slope

2. d) all of the above

3. b) ordinal scale

4. extrapolation

5.b) students who watch more TV tend to get lower marks

6.b) would still be 24

7. observational study

8. a) weather a heart attack occurred

9.b) Simpson's paradox

10. e) all of them

11. 30.5

12. ii and iii