October 31 st , 2003

1. October 31st, 2003 • Finish Quasi-experiment • True-experiment • Lit review assignments • Full text only • See reference lists of relevant articles (may require a trip to the library) • See keywords of relevant articles

2. Realistic example • Nonequivalent control • Rehab vs. no rehab conditions NCR O X O NnoCR O O • Q: Changes in reactivity to stressor • May be unethical to randomize • Assignment based on preexisting treatment

3. Realistic example • Nonequivalent control • 2 classrooms of students N O X O N O O • Behavioral intervention • Randomize which classroom gets treatment • Need separate classes to avoid resentment, migration, etc.

4. Realistic example • Other uses • CHD and no CHD comparison group NCHD O Xex O NnoCHD O Xex O • How does exercise influence?: • VO2 max change • Self-efficacy for exercise

5. True-experimental • Take 2 identical situations • Change an element in one situation • What happens? • E.g., Compare 2 cameras

6. True-experimental • Goal here is to demonstrate: • If X, then Y • If not X then not Y • Does X ‘cause’ Y? • Create identical groups of people • Random assignment is key to success!

7. True-experimental • 3 characteristic of the true experiment help rule out most threats • One or more control groups AND one or more treatment groups • Random assignment from population of interest • Variable(s) of interest can be manipulated directly

8. True-experimental R X O R O • Two group post test only • Better than previous designs • Control group • Assume randomization ensures baseline equivalence

9. True-experimental R X1 O R X2 O R O • Example • X1 70% VO2max training • X2 40% VO2max training • O is fitness

10. Multiple group post-test only • Advantage • Good for assessing differences after treatment • No threat from a pre-test • Relatively inexpensive • Disadvantages • Selection-Mortality • E.g., lack of pain treatment, or painful treatment • Don’t have a direct measure of change

11. True-experimental R O X O R O O • Classic pretest-posttest control group design • Does treatment group change more than control group? • Group by time interaction

12. True-experimental R O X1 O R O X2 O R O O • Example: • X1: 10,000 steps every day for 6 mos. • X2: ‘Traditional’ activities for 6 mos. • Control: remain on the couch • O: VO2max, Blood lipids, glucose tolerance, blood counts, etc.

13. The Classic • Advantage • Good for assessing changes after treatment • Many threats ‘controlled’ (testing, maturation, etc.) • Looks good on CV • Disadvantages • Pretest • Selection-Mortality • E.g., lack of pain treatment, or painful treatment • Diffusion of treatment • Resentment for no treatment

14. Interpreting outcomes • Outcome 1: • Both groups increase • Placebo effect? • Maturation, etc. • BUT…

15. Interpreting outcomes • Outcome 2: • Demonstrated treatment effect • Ideal case • Interaction: • Treatment by time

16. Interpreting outcomes • Outcome 3: • Main effect over time • Both groups improve • Treatment ineffective

17. Interpreting outcomes • Outcome 4: • No difference between groups or over time

18. Solomon 4-group design R O X O R O O R X O R O • Two Treatment, two no treatment • One of each is pretested • Used to control for testing threats • Does test influence post-test score

19. Trochim (1999)

20. Trochim (1999)

21. The Classic • Disadvantages • Requires 4 groups of participants • Costly • Difficult to analyze • Next time: • Advanced/ more complex designs.