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PSYC 235: Research Methods ALT DESIGN. Quasi Experiments.

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Presentation on theme: "PSYC 235: Research Methods ALT DESIGN. Quasi Experiments."— Presentation transcript:

1 PSYC 235: Research Methods ALT DESIGN

2 Quasi Experiments

3 Differences between lab and natural experiments Control Internal validity External validity Basic and applied goals Consequences Practical limitations GOALS – to ENHANCE internal and external validity

4 Control – threats to internal validity History (events other than tx) Maturation Repeated testing Instrumentation changes Regression to the mean Selection and interaction with selection Subject mortality and attrition

5 External Validity - generalizability Subjects Situations Task Time

6 Basic and applied goals

7 Subject variables: e.g. developmental research Correlation does not equal causation!!!! Cross sectional Longitudinal Time lag Cross sequential Major confounds of each

8 Combining Quasi and True IV E.g. age + ritalin, diagnosis + task difficulty, gender + video content Importance of the interaction

9 Natural Treatments – ex post facto Smoking in the psychiatric ward Improving the basic design – Non-equivalent conrtol group

10 Interrupted time series Will lowering the BAC from.1 to.08 reduce drunk-driving fatalities? Do people drink more in college than at other times )or other places)? Do women who wear more makeup make more money than women who don’t? Would eliminating PSYC 235 from the curriculum increase the number of psychology majors?

11 Small n research Nomothetic versus Idiographic Advantages of each Disadvantages of each

12 Small n: Applied Behavior Analysis Skinnerian versus statistical traditions Designs – AB – ABA – ABAB – Alternating treatments (e.g. ABCA) Example: Behavioral Contrast Multiple baseline designs

13 Psychophysical designs Signal detection theory – Discriminability (d’) – Bias (B)


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