Quazi-Experimental Designs

1. Quazi-Experimental Designs

2. Outline of Today’s Discussion • True Experiments • Quasi-experimental Designs

3. The Research Cycle Real World Research Representation Abstraction Generalization Methodology Data Analysis Research Results Research Conclusions

4. Part 1 True Experiments

5. True Experiments Three Features of a True Experiment: 1. Manipulation of Independent Variable(s) 2. High Level of Control (Treatment & Control Conditions) 3. Random Assignment To Conditions A true experiment unambiguously demonstrates what caused an outcome.

6. True Experiments • Potential Pop Quiz Question: In your own words, how does the setting (lab versus field) relate to the issue of validity (internal versus external)? • Potential Pop Quiz Question: In your own words, how does the ‘setting’ (lab versus field) relate to the goals of research (basic versus applied)?

7. True Experiments • Potential Pop Quiz Question: In your own words, explain the Hawthorne effect. http://en.wikipedia.org/wiki/Hawthorne_effect • Potential Pop Quiz Question: In your own words, explain what is meant by the word contamination, within the context of problems of (even) true experiments.

8. True Experiments • Potential Pop Quiz Question: This is a 3 part question that requires some critical thinking. A) Does ‘resentment / demoralization’ tend to increase type 1 error or type 2 error? xplain. B) Does ‘rivalry’ tend to increase type 1 error or type 2 error? Explain. C) Does ‘diffusion’ tend to increase type 1 error or type 2 error? Explain.

9. Part 2 Quasi-Experimental Designs

10. Inspired by Campbell & Stanley (1966) Quasi-Experimental Designs O1 X O2 “What’s wrong with this picture?”

11. Inspired by Campbell & Stanley (1966) Quasi-Experimental Designs • O1 X O2 • - - - - - - - - - - - • O1 O2 Would someone please walk us through this?

12. Quasi-Experimental Designs • So, we will consider three types of quasi-experimental designs. All lack the randomization (and hence the control) of a true experiment. • Non-equivalent control group design - a group that is “like” the treatment group, and that can be examined by a pre-test & post-test. • The pre-test helps to ensure at least some meaningful similarity.

13. Quazi-Experimental Designs Would someone please walk us through Langer & Rodin (1976) study with Nursing Home Residents (see PubMed)? http://www.ncbi.nlm.nih.gov/pubmed/?term=1011073

14. Quasi-Experimental Designs • The next quasi-experimental design is the interrupted time series design. • This is used when researchers have the opportunity to observe the dependent variable for considerable time periods before and after the treatment…

15. Inspired by Shadish, Cook & Campbell (2002) Quasi-Experimental Designs O1 O2 O3 X O4 O5 O6 Would someone please walk us through this?

16. Inspired by Campbell (1969) Quasi-Experimental Designs Would someone please walk us through this?

17. Quasi-Experimental Designs • Finally, the two previous quasi-experimental designs can be combined into a time series with non-equivalent control group design. • This is used when researchers have the opportunity to observe the dependent variable for considerable time periods before and after the treatment…

18. Inspired by Shadish, Cook & Campbell (2002) Quasi-Experimental Designs O1 O2 O3 X O4 O5 O6 --------------------------------------- O1 O2 O3 O4 O5 O6 Would someone please walk us through this?

19. Quazi-Experimental Designs Can someone apply the previous idea here? From McSweeney (1978) http://www.ncbi.nlm.nih.gov/pubmed/16795584

20. Quazi-Experimental Designs Arrows indicate days w/o helicopter! From Schnelle et al., 1978 http://www.ncbi.nlm.nih.gov/pubmed/16795578

22. Campbell, D.T. (1969). Reforms as experiments. American Psychologist, 24, 409-429. Campbell, D.T. & Stanley, J.C. (1966). Experimental and Quasi- Experimental designs for research. Chicago, Rand McNally. Shadish, W.R., Cook, TD., & Campbell, D.T. (2002). Experimental and quasi-experimental designs for generalized causal inference, Boston, Houghton Mifflin.