1. 7-2 Correlation Coefficient Objectives Determine and interpret the correlation coefficient.

2. Correlation Coefficient - Facts Correlation coefficient is always between -1 and +1. –Weak correlation is closer to zero and strong correlation is closer to either -1 or +1. Ex. r = 0.21 or -0.21 (weak), r = -0.98 or 0.98(strong). –If correlation is equal to exactly -1 or +1 then the data points all fall on an exact straight line.

4. r = +.3r = +1 Examples of Approximate r Values y x y x y x y x y x r = -1 r = -.6r = 0

5. r =1 1. Estimate the correlation coefficient (r-value).

7. 2. Estimate the correlation coefficient (r-value). r =-1

8. 3. Estimate the correlation coefficient (r-value).

9. r = 0.95

10. 4. Estimate the correlation coefficient (r-value). r =-0.95

11. 5. Estimate the correlation coefficient (r-value).

12. r = 0.6

13. 6. Estimate the correlation coefficient (r-value). r = -0.6

14. Correlation Coefficient 7. Estimate the correlation coefficient (r-value). r = 0.9

15. Correlation Coefficient 7. Estimate the correlation coefficient (r-value).

16. Correlation Coefficient 8. Estimate the correlation coefficient (r-value).

17. Correlation Coefficient 8. Estimate the correlation coefficient (r-value). r = 0.4

18. Correlation Coefficient 9. Estimate the correlation coefficient (r-value).

19. Correlation Coefficient 9. Estimate the correlation coefficient (r-value). r = 0

20. 10. a)draw a scatter plot of the data b) draw in the best fit line X1525354555 Y4136353330 15 20 25 30 35 40 45 50 55 60 65 70 30 32 34 36 38 40

21. 10. a)draw a scatter plot of the data b) draw in the best fit line X1525354555 Y4136353330 15 20 25 30 35 40 45 50 55 60 65 70 30 32 34 36 38 40

22. 10. c) find the equation of your best fit line 15 20 25 30 35 40 45 50 55 60 65 70 30 32 34 36 38 40 42 44 1 45 50 55 0 5 10 Y-intercept 45 -4 15 Slope

23. 10. d) estimate y when x = 20 15 20 25 30 35 40 45 50 55 60 65 70 30 32 34 36 38 40 42 44 1 45 50 55 0 5 10 About 40

24. 11. Find the correlation Coefficient X1525354555 Y4136353330 15 20 25 30 35 40 45 50 55 60 65 70 30 32 34 36 38 40

25. Classwork/Homework 7-2 Worksheet