1. Jackson, even-numbered Chapter Exercises, pp. 335-337.
2. Explain the difference between multiple independent variables and multiple levels of independent variables. Which is better?
3. What is blocking and how does it reduce “noise”? What is a disadvantage of blocking?
4. What is a factor? How can the use of factors benefit a design?
5. Explain main effects and interaction effects.
6. How does a covariate reduce noise?
7. Describe and explain three trade-offs present in experiments.
Week 5
Quasi-Experimental Designs
Part I – Answer the following questions:
1. Jackson (2012), even-numbered chapter exercises, p 360.
2. Describe the advantages and disadvantages of quasi-experiments? What is the fundamental weakness of a quasi-experimental design? Why is it a weakness? Does its weakness always matter?
3. If you randomly assign participants to groups, can you assume the groups are equivalent at the beginning of the study? At the end? Why or why not? If you cannot assume equivalence at either end, what can you do? Please explain.
4. Explain and give examples of how the particular outcomes of a study can suggest if a particular threat is likely to have been present.
5. Describe each of the following types of designs, explain its logic, and why the design does or does not address the selection threats discussed in Chapter 7 of Trochim and Donnelly (2006):
a. Non-equivalent control group pretest only
b. Non-equivalent control group pretest/posttest
c. Cross-sectional
d. Regression-Discontinuity
6. Why are quasi-experimental designs used more often than experimental designs?
7. One conclusion you might reach (hint) after completing the readings for this assignment is that there are no bad designs, only bad design choices (and implementations). State a research question for which a single-group post-test only design can yield relatively unambiguous findings.
Part II – Answer the following questions:
1. What research question(s) does the study address?
2. What is Goldberg’s rationale for the study? Was the study designed to contribute to theory? Do the results of the study contribute to theory? For both questions: If so, how? If not, why not?
3. What constructs does the study address? How are they operationalized?
4. What are the independent and dependent variables in the study?
5. Name the type of design the researchers used.
6. What internal and external validity threats did the researchers address in their design? How did they address them? Are there threats they did not address? If so how does the failure to address the threats affect the researchers’ interpretations of their findings? Are Goldberg’s conclusions convincing? Why or why not?
Week 6   