1. Matched Pairs t Tests SPSS

2. Source of the Data  Cognitive-behavioral intervention to reduce African American adolescents' risk for HIV infection Cognitive-behavioral intervention to reduce African American adolescents' risk for HIV infection  Group EC was given a standard 2-hour educational program  Group BST went through an 8 week behavioral skills training program.

3. The Dependent Variables The log-transformed frequency of condom- protected sexual intercourse Measured before the intervention, at posttest (8 weeks later), 6 weeks after posttest, and 12 weeks after posttest.

4. A Plot of the Means

5. Download the Data  http://core.ecu.edu/psyc/wuenschk/SPSS/ MAN_1W2B.sav http://core.ecu.edu/psyc/wuenschk/SPSS/ MAN_1W2B.sav  Bring the data into SPSS  We want to do two matched pairs t tests  One for the EC group  One for the BST group

6. Split the File by Group  Data, Split File

7. Conduct the Test Analyze, Compare Means, Paired Samples T Test, Pretest versus fu6

10. Obtain Estimates of Cohen’s d Download the.sav and.sps files  D-EqN-- Estimate Cohen's d, equal n data (including correlated samples)  d-EqN-Doc -- instructions d-EqN-Doc  d-EqN-Dat -- necessary data file d-EqN-Dat  d-EqN-Run -- syntax file d-EqN-Run

11. Enter Statistics Into.sav File

12. Run the Syntax File

13. Look Back at.sav File

14. Summary Statement, BST Adolescents in the behavioral skills training group (n = 20) engaged in significantly more condom-protected intercourse six weeks after the training (M = 18.80, s = 11.04) than prior to the training (M = 13.45, s = 13.77), t(19) = 2.35, p =.030, d =.43.

15. Summary Statement, EC Adolescents in the educational control group (n = 20) engaged in significantly less condom-protected intercourse at the six week followup (M = 8.60, s = 11.09) than at pretest (M = 19.8, s = 21.87), t(19) = 2.40, p =.027, d =.65.