1. Wed Oct 29, 2003 Exams after class Mean(SD): 71.6(11.6)% Range: 44-95% Appointment Research day 1 week

2. Distribution

3. Quasi-experimental Have one or more: manipulated variables (X) Outcome variables (O) No random assignment Pre-assigned groups Ethical or practical reasons CHD vs. No-CHD Smoker vs. non-smoker Better example: CR vs no-CR

4. Quasi-experimental Non-equivalent control group design Better than previous designs Control group, pre & post-tests More confidence in causal inferences O X O --------- O

5. Problems with this design Selection bias Most participants self-selected Pre-existing groups Can affect pre-test scores Maturation History regression

6. Interpreting outcomes Outcome 1: Selection threat Maturation? History? Treatment group Not control

7. Interpreting outcomes Outcome 2: Selection History Maturation

8. Interpreting outcomes Outcome 3: Selection Large decline? Regression Example?

9. Interpreting outcomes Outcome 4: Selection Large increase? Regression Example?

10. Interpreting outcomes Outcome 5: Clearest evidence of successful intervention Unlikely to change faster with lower baseline

11. Quasi-experimental O 1 O 2 O 3 X O 4 O 5 O 6 Interrupted time-series Similar to pre & post test design Multiple pre & post-test measures Increased confidence in baseline and outcome data Selection, maturation, history

12. Outcomes of interrupted… Treatment

13. Quasi-experimental O 1 O 2 O 3 X O 4 O 5 O 6 X O 7 O 8 O 9 Interrupted time-series with removal To show change with X and change with removal of X e.g., drug regimen, knee brace, etc. Question of ethics (removal of X) Should be a quick treatment response

14. Quasi-experimental Interrupted time-series with non- equivalent control Stronger that non-equivalent control More confidence in pre & post-test measures Strongest Quasi design? O 1 O 2 O 3 X O 4 O 5 O 6 -------------------------- O 1 O 2 O 3 O 4 O 5 O 6