Discrete Quiz Chapter 6

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1. An outlier is an individual value that: A) extends the pattern. B) deviates from the pattern. C) determines the strength of the relationship. D) outlines the general form of the data. Ans: B

2. If two variables are both positive, and tend to be linked so that growth of one variable tends to indicate growth in the other variable, then: A) the variables are positively associated. B) the variables are negatively associated. C) the variables have no association with each other. Ans: A

3. If a regression line for two variables has a small positive slope, then: A) the variables are positively associated. B) the variables are negatively associated. C) the association of the variables cannot be determined. D) the variables have no association with each other. Ans: A

4. If two variables are negatively associated, then the regression line: A) has a negative intercept. B) has a negative slope. C) has negative coefficients. D) is valid for only negative values. Ans: B

5. If the regression line is 2x + 4y = 10, then the variables: A) have a positive association. B) have a negative association. C) have an association that is sometimes positive and sometimes negative. Ans: B

6. If the variables have a negative association, then their correlation: A) must be less than 1. B) must be between 1 and 0. C) must be between 0 and 1. D) must be greater than 1. Ans: B

7. If the correlation between two variables is 1, then the points of their scatterplot: A) all lay within 1 unit of the regression line. B) all lay within ½ unit of the regression line. C) all lay on the regression line. D) lay so that exactly half of the points are on each side of the regression line. Ans: C

8. If the units of measurement change to larger units, then the correlation: A) becomes larger. B) becomes smaller. C) does not change. Ans: C

9. The intercept of the least-squares regression line is A) the mean of the y values. B) the mean of the x values. C) the mean of the y values minus the mean of the x values. D) none of these. Ans: D

10. If the least-squares regression line is y = 3x -5, then for y= 2, the predicted value for x is: A) 1. B) 3. C) 2 1/3. D) 6. Ans: C

11. If the least-squares regression line is y = 5x  3, then for x = 3, the predicted value for y is: A) 2. B) 0. C) 1 1/5. D) 12. Ans: D Use the following scatterplot to answer questions 12-13.

12. For the scatterplot shown below, what can you say about the least-squares regression line?

A) Its slope is positive. B) It passes through the point (0,0) C) It stops at y = 800 D) None of these Ans: A

13. For the scatterplot shown below, what can you say about the correlation?

A) It is almost 0. B) It is between 0 and 1. C) It is exactly 1. D) It is greater than 1. Ans: B Use the following scatterplot to answer questions 14-15.

14. What can you say about the slope of the least-squares regression line?

A) The slope is zero. B) The slope is positive. C) The slope is negative. D) The slope varies. Ans: B

15. What can you say about the correlation?

A) The correlation is greater than 1. B) The correlation is exactly 1. C) The correlation is between 0 and 1. D) The correlation is negative. Ans: C

16. Suppose the points of a scatterplot lie close to the line 3x + 2y = 6. The slope of this line is: A) 3. B) 2/3. C) 3/2. D) 3/2. Ans: D 17. For professional baseball players, one would expect a negative correlation between: A) batting average and salary. B) years of play and salary. C) number of home runs and salary. D) number of errors and salary. Ans: D

18. A typing service keeps data on the number of pages in a manuscript and the length of time (in hours) it takes to complete the typing. The least squares regression line for the data is given by y = 20 + 0.273x. Use this to predict the length of time needed to type a 40-page manuscript. A) 810.92 B) 60.273 C) 30.92 D) 16.38 Ans: C

19. A bank collects data on the savings and incomes of families to predict an expected increase in certificate of deposit accounts due to a 10% increase in salaries of employees at a local company. Which variable, savings or income, would be the explanatory variable? A) Family savings B) Family income Ans: B

20. A university admissions counselor wishes to predict the performance of freshmen by considering their SAT scores. Which variable, freshman GPA or SAT score, would be the explanatory variable in a least squares regression equation? A) Freshman GPA B) SAT score Ans: B

21. Max is collecting baseball cards. He has 65 that his aunt gave him for his birthday, and he buys 20 more each week. The total number y of cards that Max has after x weeks is given by which of the following equations? A) y = 20 + 65x B) y = 65 + 20x C) y = 20 + x D) y = 85x Ans: B (For number 22 use the data given below)

22.What is the correlation between the variables?

A) About 0.99 B) About 0.94 C) About 0.70 D) About 0.50 Ans: B

Temperature in 70 72 74 75 81 82 degrees F (y) Chirps per 15 15 15 16 17 17 second (x)

(For number 23 use the data given below)

Let x = time spent studying and y = test score.

Time spent 1 2 5 4 6 7 8 5 2 4 3 5 studying (hours) Test score 49 57 80 70 88 91 98 80 57 72 65 82 (percentage)

23. What is the expected test score if three hours are spent studying?

A) About 63 B) About 65 C) About 67 D) About 70 Ans: B

24. If the x and y coordinates of a scatterplot are exchanged, the correlation of the variables: A) remains unchanged. B) changes to its reciprocal. C) changes to its negative reciprocal. D) none of these. Ans: A

25. If the x and y coordinates of a scatterplot are exchanged, variables which were previously positively associated: A) remain positively associated. B) are now negatively associated. C) are no longer associated. Ans: A