Modes of Observations (Research Designs) –Experiments –Survey Research –Field Research –Unobtrusive Research –Evaluation Research Each of these methods have different strengths and weaknesses –And different areas where they are more or less useful

Criteria for establishing causation in the social sciences –Establish a relationship –Establish time ordering –Rule out spuriousness How do experiments do these things?

Critical Components of Experiments Independent and Dependent Variables –The “cause” is the experimental manipulation Pre-test and Post-test Experimental and Control Groups –RANDOM ASSIGNMENT NOTE: This is different from random sampling –Generalization (random sampling) –Rule out spuriousness (random assignment)

The “Classic” Experimental Design Treatment Group PretestTreatmentPosttest Control Group Pretest(Placebo)Posttest SUBJECT POOL RANDOM ASSIGNMENT TIME

The Subjects Selection of a subject pool –Effects the extent to which experimenter can generalize Difficult to do “random sample” (must “recruit” subjects). BUT  less of an issue for explanatory research Still, “Mice versus Men” (Or Men vs. Women) Assignment of subjects to groups –Randomized –Matching

Close, but no cigar… Experimental designs that fall short The One-Shot case study The One-Group pretest-posttest design The Static-Group comparison NOTE –Sometimes, to capitalize on “natural,” phenomena, research will do these “quasi-experiments” and try to rule out threats to internal validity

Other Important Considerations Placebo –The “Hawthorne effect” Double Blind Experiments –Neither subjects (this is typically the case) nor experimenters are aware of who is in the control or experimental group

Threats to Internal Validity History Maturation Testing Instrumentation Statistical regression Selection bias Experimental mortality Demoralization

External Validity External validity = generalizability –“Laboratory experiments” versus “the wilds of society” –Example: the effect of “pre-testing” on subjects Subjects (both control and experimental) become sensitized to the independent variable –Results may not “work” in real world because people are sensitized in the same way –Solution: “Solomon Four-Group Design” (or better yet, no pre- testing at all). Experiments in general are “artificial” and are suspect with regard to generalizability

Natural Experiments Sometimes called “quasi-experiments” –They lack one or more of the hallmarks of the classic experimental design Death penalty research Low birth-weight study Study of nuclear power plants Prejudice and Roots Evaluation research often uses quasi- experimental designs

Experiments Review and Summary –Classic experimental design (not used as posttest only) Random assignment as key –Advantages of Experimental Design? –Disadvantages?

How does an experimental design… –Establish a relationship –Establish time ordering –Rule out spuriousness