Psychology 2300 Chapter 12 Small N Designs provide a lot of information from a few people Case Studies an intensive description and analysis of a single case o Can be an individual a group or an organization o Types of Case Studies Snapshot case done within a single time period Longitudinal case done over time as key variables change naturally Intervention case done over time with a planned or unplanned change Example treatment of disease with new medication o Advantages of Case Studies Rich source of ideas for developing research questions Provide rationale not conclusion Can provide tentative evidence in support of a theory Can provide evidence against a theory Useful method for studying a rare event Useful way to try out and examine a new treatment o Disadvantages of Case Studies Observer biases likely Possibility of demand characteristics and expectancy effects Extremely limited internal validity Limited external validity o Ways to Strengthen Case Studies Conduct multiple case studies Replicate the case study Meta analysis combine several different case studies on the same phenomena If a treatment is being examined select other cases that vary on variables of interest Gender of the client Theoretical orientation of the therapist Problem being treated Expand case study to a single case experimental design Single Case Experimental Designs a type of within subject design with intensive examination of one person over time in controlled conditions 1 Stable Baseline Design Measure dependent variable and establish stable baseline Introduce treatment independent variable and measure dependent variable Compare baseline and treatment stage 2 Reversal Design Alternate baseline A and treatment B conditions Change in dependent variable from baseline A to treatment B back to baseline A and so forth Provides support for effects of treatment If behavior reverts to baseline after treatment is discontinued then we have evidence for effectiveness of treatment In essence we are creating replication within the experiment o Explanations for Lack of Return to Baseline in Reversal Design Treatment is such that effect continues even when treatment is withdrawn Variable confounded with first treatment May also be ethical issues in removing an effective treatment for example self injurious behavior in children Multiple Baseline Design establishes multiple baselines of behavior can be in different settings o Introduce treatment in one setting at a time and record effects o Strong support for effects of treatment if Baselines remain stable in all settings before treatment applied in that setting Behavior changes as predicted after treatment applied in each setting Best when 3 4 baselines are used o Advantages over stable baseline or reversal design Replications are built into the design Replication across settings and time strengthens external validity Can be used when removing a treatment is impractical or unethical o One problem effects may generalize across settings before treatment introduced