correlation

1. correlation Are two variables related? 1. Do they move together or opposite? 2. How strongly? (if they are strongly related, we can predict one from the other)

2. correlation coefficient NO ASSN NEGATIVE POSITIVE -1.00 0 +1.00 = direction + / - number = strength

3. sign (+ or -) move together or opposite? positive correlation + negative correlation -

4. positive correlation Variable 1 Variable 2 # of shoes you own amt of credit card debt move together, in same direction

5. correlational studies POSITIVE NEGATIVE NO ASSN

6. Are shy people happy? To a group of people, give a questionnaire about their degree of shyness. To this same group, give a questionnaire about their degree of happiness. Each person has two scores. Use correlation. Is there a relationship between shyness & happiness? (Did one cause the other?)

7. correlational studies Correlation is NOT causation! B A B A A C B

8. example Variable 1 Variable 2 ice cream sales violent crime Ice cream sales positively correlate with the occurrence of violent crime. e.g.

9. example Variable 1 Variable 2 # parties at your house # of friends linked at Facebook # parties at your house positively correlate with # of friends linked at Facebook e.g.

10. correlation coefficient NO ASSN NEGATIVE POSITIVE -1.00 0 +1.00 = direction + / - = strength number weak (0 - .40) moderate (.41 - .69) strong (.70 – 1.00)

11. correlation coefficient NO ASSN NEGATIVE POSITIVE -1.00 0 +1.00 = direction + / - = strength number

12. correlation coefficient NO ASSN NEGATIVE POSITIVE -1.00 0 +1.00 = direction + / - = strength number

13. real examples Variable 1 Variable 2 +.90 height of twin #1 height of twin #2 +.50 marriage problems behavioral problems in children +.45 height of sister #1 height of sister #2 +.20 exposure to violent media real-life violent behavior -.40 amt of social support frequency of illness

14. experimental research Hypothesis: Systematic desensitization therapy eliminates phobias. DEPENDENT VARIABLE INDEPENDENT VARIABLE