SMALL-N DESIGNS

1. SMALL-N DESIGNS • Experiments conducted on only one or a few subjects • External validity is a problem • Internal validity is often very good - no individual differences • Available population may be small

2. Reversal Designs • Measure before treatment, with treatment, and after treatment is removed or reversed (ABA Design) • The treatment is the independent variable • Measure the dependent variable at each stage of the design

3. Reversal Designs • Not appropriate for treatments with permanent effects • Variations: • ABAB • ABBA

4. Multiple Baseline Designs • Compare before and with treatment; use other behaviors, situations, or subjects as baselines • Useful when treatment has permanent effect

5. Multiple Baseline: Behaviors Behavior 1 before / Behavior 1 after Behavior 2 before ………. / Behavior 2 after Behavior 3 before ……………… TIME

6. Multiple Baseline: Situations Situation 1 before / Situation 1 after Situation 2 before ………. / Situation 2 after Situation 3 before ……………… TIME

7. Multiple Baseline: Subjects Subject 1 before / Subject 1 after Subject 2 before ………. / Subject 2 after Subject 3 before ……………… TIME

8. Statistics for Small-N Designs • Inferential statistics are not used • Use descriptive statistics; show data graphically