1. Scatterplots Represent two variables at once Show the relationship between X and Y Y X trust love

2. Why look at relationship? Predict Y from X Test theory that X causes Y Examine possible connection between X and Y

3. How to see relationships Divide X axis into bands Examine average Y in each band Does it change between bands?

4. Income (Y) & Education (X)

5. What could we tell? As education went up, average income increased. Was it uniform? How much increase in average income was there between education levels?

6. Income (Y) & Age (X)

7. What could we tell? Did the average income increase for older groups of person? Was it uniform? How much change was there?

8. Note In both cases of income and education and of income and age, as one increased the other increased. Increase in X -- Increase in Y This is a positive relationship

9. Depression and Self-esteem

10. What could we tell? Did the average depression decrease for groups of persons with higher self- esteem? Was it uniform? How much change was there?

11. Marital Commitment and Disagreements

12. What could we tell? Did the average marital commitment decrease for persons with more disagreements? Was it uniform? How much change was there?

13. Note As X increased, Y decreased Bigger X, smaller Y This is a negative relationship - also called an inverse relationship

14. Why are X and Y related? X causes Y Y causes X X and Y are caused by W X X X Y Y Y W

15. How strong is the relationship? Two meanings to strength of relationship Substantive: how much change in Y for a given change in X How much increase in income for one additional year of school? Statistical: how much random variation around the relationship line is there? Does everyone’s income increase the same amount for one more year of education?

16. Relationship Outliers