Single- Subject Research Designs

Chapter 14

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Single- subject designs

Single- subject designs, or single- case designs, are research designs that use the results from a single participant or subject to establish the existence of cause- and- effect relationships.

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Phases and phase changes

A phase is a series of observations of the same individual under the same conditions.

When no treatment is being administered, the observations are called baseline observations.

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Visual Inspection Techniques

• Unfortunately, there are no absolute, objective standards for determining how much of a change in pattern is sufficient to provide a convincing demonstration of a treatment effect.

• The most convincing results occur when the change in pattern is immediate and large.

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4 types of change

• Change in average level• Immediate change in level• Change in trend• Latency of change.

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Change in average level Change in trend

Immediate change in level Latency in Change

The problem with single subject design

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THE ABAB REVERSAL DESIGN

• the majority of single- subject research studies use ABAB design;

• consists of four phases: a baseline phase ( A), followed by treatment ( B), then a return to baseline ( A), and finally a repetition of the treatment phase ( B).

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Effective

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A= no treatment

Not Effective

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Variations on the ABAB Design

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1- B&B1 not working use C

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2- B not working add C

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B= Graduated exposureC= Reinforcement

3- MULTIPLE- BASELINE DESIGNS

1- Eliminates the need for a return to baseline and therefore, 2- Is particularly well suited for evaluating treatments with long- lasting or permanent effects.

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3- MULTIPLE- BASELINE DESIGNS

ExamplesA therapist uses the same method for 2 different behaviors (across behaviors)For one behavior that is exhibited in 2 different situations. (across situations)A teacher uses the same method on 2 different individuals (across subjects)

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2 different students

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Person1

Person2

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Yelling

Crying

2 different behaviors

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School

2 different situations.

Home

Weaknesses of the Multiple- Baseline Design?

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4- Dismantling design

A dismantling design, also called a component- analysis design, consists of a series of phases in which each phase adds or subtracts one component of a complex treatment to determine how each component contributes to the overall treatment effectiveness.

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Example

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5- The Changing- Criterion Design

• The criterion level is changed from one phase to the next.

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Smoking Treatment

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6-The Alternating- Treatments Design

• In an alternating- treatments design, also called a discrete-trials design, two ( or more) treatment conditions are randomly alternated from one observation to the next.

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Example - Alternate weeks

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Group Discussion

• Suppose you are interested in performing an observational study of kindness (kind behavior) among students in a school. Describe one method to quantify this behavior: that is, explain how you could convert the observations into numerical scores.

• In most research studies, statistical techniques are used to rule out chance as a plausible explanation for the results. In single-subject research, how is chance (or coincidence) ruled out as a plausible explanation for the observed treatment effects?