Within Subjects Designs Small N Instructor Marci Smith

Within Subjects Designs: Small N Instructor- Marci Smith mercury 1@uab. edu

Small N Designs n n Small N designs- a design in which just one or a few subjects are used; typically, the experimenter collects baseline during and initial control condition, applies the experimental treatment, then reinstates the original control condition to verify that changes observed were caused by the experimental intervention. Baseline- a measure of behavior as it normal occurs without the experimental manipulation; a control condition used to assess the impact of the experimental condition.

Why would we use small N? n It can be argued that aggregate (average) effects are artificial because they do not represent what really occurs with any individual subject; large N reveals general trends, which might not produce reliable conclusions.

Why would we use small N? n When looking at pooled data (averages) it is possible that subjects responses cancel each other out, giving the appearance of no effect.

Why would we use small N? n The results of aggregates (average) might not be a good reflection of the reaction of individual subjects.

Why would we use small N? Sometimes its not possible to find a large number of subjects, particularly when examining disease states such as schizophrenia. n Animal research often uses small N because animals are expensive to maintain and when sacrificing animals you want to use as few as possible. n

AB Design n AB design- a design in which a baseline condition (A) is measured first, followed by measurements during the experimental condition (B).

ABA Design n ABA design- a design in which a baseline condition (A) is measured first, followed by measurements during the experimental condition (B), followed by a return to baseline condition (A) to verify that the change in behavior is linked to the experimental condition. This is also called a reversal design.

ABAB Design n ABAB design- a design in which a baseline condition (A) is measured first, followed by measurements during a treatment condition (B), followed by a return to the baseline condition (A) to verify that the change in behavior is linked to the experimental condition, followed by a return to the treatment condition.

ABABA n ABABA design- a design in which a baseline condition (A) is measured first, followed by measurements during a treatment condition (B), followed by a return to the baseline condition (A), followed by a return to the treatment condition (B) and a final baseline measurement condition (A) to verify that the change in behavior is linked to the experimental condition.

Multiple Baseline Design n Multiple baseline design- in which a series of baselines and treatments are compares within the same person, but once a treatment is established it is not withdrawn.

Changing Criterion Design n Changing criterion design- a design used to modify behavior when the beahvior cannot be changed all at once; instead, the behavior is modified in increments, and the criterion for success (reinforcement) changes as the behavior is modified.

Discrete Trials Design n Discrete trials design- a design that relies on presenting and averaging across many, many experimental trials repeated application result in a reliable picture of the effects of the IV.

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