9.2 EXERCISES 490 CHAPTER 9 Correlation and Regression For Extra Help: MyLab Statistics Building Basic Skills and Vocabulary 1. What is a residual? Explain when a residual is positive, negative, and zero. 2. Two variables have a positive linear correlation. Is the slope of the regression line for the variables positive or negative? 3. Explain how to predict y@values using the equation of a regression line. 4. For a set of data and a corresponding regression line, describe all values of x that provide meaningful predictions for y. 5. To predict y@values using the equation of a regression line, what must be true about the correlation coefficient of the variables? 6. Why is it not appropriate to use a regression line to predict y@values for x@values that are not in (or close to) the range of x@values found in the data? In Exercises 7–12, match the description in the left column with its symbol(s) in the right column. 7. The y@value of a data point corresponding to xi a. nyi b. yi c. b d. 1x, y2 e. m f. y 8. The y@value for a point on the regression line corresponding to xi 9. Slope 10. y@intercept 11. The mean of the y@values 12. The point a regression line always passes through Graphical Analysis In Exercises 13–16, match the regression equation with the appropriate graph. 13. ny = -1.361x + 21.952 14. ny = 2.115x + 21.958 15. ny = 2.125x + 9.588 16. ny = -0.705x + 27.214 a. x y 5 10152025303540 5 10 15 20 25 30 b. x y 2 4 6 8 10 5 10 15 20 25 30 c. x y 10 20 30 40 50 20 40 60 80 100 120 140 d. x y 5 1015202530 10 20 30 40 50 60 70
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