1. Unit 2: Bivariate Relationships Lesson 2: Covariance and Pearson r EDER 6010: Statistics for Educational Research Dr. J. Kyle Roberts University of North Texas Next Slide
2. Covariance Are The Variables Correlated??? “ The average cross-product of the deviation scores.” Answers 2 Questions: 1. Is there any relationship between X and Y? 2. If there is a relationship, is it positive or negative? Next Slide
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4. Pearson r “ The average cross-product of the standardized deviation scores.” Answers 3 Questions: 1. Is there any relationship between X and Y? 2. If there is a relationship, is it positive or negative? 3. How well does one line describe the data? Next Slide
5. Pearson r “ How well does a single line represent my data?” r = .85 r = -.25 r = 1.0 Next Slide
6. Pearson r r = .00 Next Slide X 0 0 1 1 Y 0 1 0 1
7. “Guessing” Pearson r Height and weight Moderate Positive SES and Math Achievement High Negative Tobacco use and Life Expectancy High Positive GPA and SAT Near Zero Shoe size and IQ Moderate to High Positive Next Slide Parameters Pearson r
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9. Square Before You Compare R 2 = .25 R 2 = .36 “ Study 2 explains 11% more variance than Study 1” Next Slide Study 1 Pearson r between GPA and GRE r = .50 Study 2 Pearson r between IQ and GRE r = .60
10. A Little Practice r = 1.0 r = .832 Next Slide X 5 6 7 8 9 Y 10 12 14 16 18 X 5 6 7 8 9 Y 10 12 14 16 14
11. Unit 2: Bivariate Relationships Lesson 2: Covariance and Pearson r EDER 6010: Statistics for Educational Research Dr. J. Kyle Roberts University of North Texas
