PSYC 235: Research Methods ALT DESIGN

Quasi Experiments

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

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

External Validity - generalizability Subjects Situations Task Time

Basic and applied goals

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

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

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

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?

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

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

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