Single Subject Designs:
Single Subject Designs How does it work? Observe an individual for while, measuring the target behavior on a set schedule. Once things are stable, introduce a treatment. Continue to observe and measure in the same way to see what happens.
Baseline Phase:
Baseline Phase Usually designated as “A” Need at least 3 data points (to establish a plateau) Observe unobtrusively (to reduce reactivity)
Following Phases:
Following Phases Each successive phase gets a new letter (e.g., B, C) Phase changes when you do something different. Try to hold everything else constant when you change something.
AB Design:
AB Design Vertical line shows point in time where baseline “A” became treatment “B” Time is on X axis, score is on Y axis. Example Weakness is threats of maturation and history.
ABAB Design:
ABAB Design Provides control for threats of history and maturation. Shows causality more clearly than AB design See 2 nd graph Figure 11.5 (2 nd graph of tactile graph figure 2) Cannot be used for behaviors that are not easily “unlearned” or when withdrawing treatment would be unethical (e.g., self injurious behavior)
Multiple Baseline Design:
Multiple Baseline Design If you can’t withdraw treatment, add a baseline. Essentially a set of stacked AB designs Controls for threat of history and maturation
Interpreting Results:
Interpreting Results Accomplished visually Provides preliminary information on the possible effect of treatment Findings need to be taken with much caution. After all, it is simply a description of what happened to one person (or a few persons) Replications could help generalize the results (although we can’t make claims in probabilistic terms).