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SMALL-N DESIGNS. What is a Small-N Design?. Experiment conducted on only one or a few subjects. Available population may be small. Internal validity is often very good - no individual differences. External validity is a problem. What is a Reversal Design?.
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What is a Small-N Design? • Experiment conducted on only one or a few subjects. • Available population may be small. • Internal validity is often very good - no individual differences. • External validity is a problem.
What is a Reversal Design? • 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.
What is a Reversal Design? • Not appropriate for treatments with permanent effects • Variations: • ABAB • ABBA
What is a Multiple Baseline Design? • Compare before and with treatment; use other behaviors, situations, or subjects as baselines. • Useful when treatment has permanent effect.
Multiple Baseline: Behaviors Behavior 1 before / Behavior 1 after Behavior 2 before ………. / Behavior 2 after Behavior 3 before ……………… TIME
Multiple Baseline: Situations Situation 1 before / Situation 1 after Situation 2 before ………. / Situation 2 after Situation 3 before ……………… TIME
Multiple Baseline: Subjects Subject 1 before / Subject 1 after Subject 2 before ………. / Subject 2 after Subject 3 before ……………… TIME
How Are Small-N Designs Analyzed? • Inferential statistics are not used. • Use descriptive statistics; graph data for each individual participant.