Single Subject Designs

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Chapter 13

• Single Subject Designs

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Single subject designs use the results from a
single participant to establish cause and effect.
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History and Modern Use

• Single subject designs has its origins in
  behavioral psychology
• Modern use in
• Experimental Analysis of Behavior
• Behavior Modification
• Assessment of Clinical Treatments

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Phases in Single Subject Research

• Baseline phase behavior observed before
  administration of a treatment to determine
  baseline
• Treatment phase behavior observed after a
  treatment has been administered
• Phase change a change in phase from baseline to
  treatment or visa versa

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Example
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Treatment phase could produce lower level of
responding
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Treatment Phase can also bring about a change in
the trend
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Another change in trend
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Identifying the change in level of behavior or
trend requires a visual analysis of the graphs.
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Things to look for when identifying treatment
effects

• Change in mean level of responding
• Immediate change in level
• Immediate change in trend

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Example Change in mean level of responding
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Example immediate change in level of responding
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Example Immediate change in trend
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Sometimes treatment effects can be masked by
unstable data
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Ways of dealing with unstable data

• Collect data until the data stabilize.
• Average across observational periods
• Look for patterns within the inconsistency

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A pattern within the instability
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Practical vs. statistical significance
With group designs, tests of statistical
significance help us overcome the problems
associated with variability (or instability) in
the data. That is not possible for single
subject designs.
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Practical vs. statistical significance
With single subject designs, the
researcher/practitioner must make a judgment
about whether the change is of practical
significance.
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Factors influencing the decision to change phases

• Is the baseline trend moving in the desired
  direction? If yes, do not change phases.
• Is the baseline at a level that is dangerous to
  the participant? Change phases immediately.
• Is the treatment resulting in a deterioration of
  the behavior? Return to baseline phase

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The ABAB reversal design

• Baseline phase (A) followed by
• Treatment phase (B) followed by
• Return to baseline phase (A) followed by
• Return to treatment phase (B)

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Sample patterns
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The design allows one to determine if the
treatment effect is replicable. If it
replicable, it implies that the treatment caused
the change in behavior.
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Problems with the design

• It wont work for treatments that have long
  lasting or permanent effects.
• It might be considered unethical in a clinical
  setting to withdraw a treatment if it was having
  a beneficial effect.

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Other single subject designs
An example from the text ABB1AC
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Other single subject designs
An example from the text ABB1AC The
researcher/practitioner can adjust the treatments
as he or she chooses
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Advantages and disadvantages of the single
subject design

• Advantages
• Can easily be used in clinical settings to
  evaluate therapy
• It is flexible in that the researcher/practitioner
  can adjust the treatments
• Disadvantages
• As with case studies, the external validity might
  be weak
• Lack of statistical analysis