1 Single Subject Experimental Design The Evidence in EBP.
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Transcript of 1 Single Subject Experimental Design The Evidence in EBP.
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Evidence-Based Practice (Sackett D et al. 2000)
• "Evidence-based medicine is the integration of best research evidence with clinical expertise and patient values."
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Evidence Based Practice Model
• To provide high-quality services
• by the integration of: – clinical expertise, – best current evidence,
and – client values
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"evidence is never enough"
• the EBP framework acknowledges that the experiences, values, and preferences of ourselves and our patients
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Efficacy encompasses
• Effectiveness– Behavior change as a direct result of
intervention
• Efficiency– Comparison of at least 2 effective treatment
interventions, in terms of one more criteria: time, cost, error rate
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Designs in Single-Subject Studies
• Phases– A phase – baseline– B phase – condition
• 2 Types of SSD– Descriptive
• A: Baseline only• B: Intervention only• A-B: Baseline-Intervention
– Experimental (control)• Examine cause-effect relationship
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Problem with A-B Design
• Does not allow the evidence to rule out the threats to internal validity
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Internal Validity
• Did in fact the experimental conditions make a difference in this specific instance?
• Threats to internal validity– Maturation/recovery– History (previous intervention)– Hawthorne Effect (testing effect)
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ABA Design• ABA design superior
to AB design• Demonstrates
experimental control through introducing and withdrawing intervention
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Potential Problems - ABA Design
• Design not common due to: – ethical issues– behavior not subject to
changes on withdrawal
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Reversal Design is applied when?
• Removal of experimental contingencies does not result in a return back to baseline
• Reversal is the application of experimental contingencies to an alternate behavior incompatible with the target behavior
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ABAB Design – Example 1
• Solves ethical issue• Vaugh & Horner (1995)
– Effects of concrete (symbol + spoken words) versus verbal modes for choice making
– A: meal choices – verbal– B: choices – picture + verbal– Resulted in more
acceptances with B phase
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ABAB Design – Example 2
• Rotholz et al (1989)– 2 communication modes
for requesting fast food– A- Choices w/ sign
language– B – Graphic symbols– Results use of graphic
symbols resulted in more successful requests than signing in community settings
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Multiple Baseline Design• Intervention is
introduced sequentially across multiple baselines:– Behaviors– Settings– Subjects
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Experimental Control in MBD
• comes with replication of intervention effects on another behavior (or subject), not a reversal or withdrawal of intervention
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How to Study Efficiency
– Comparison of at least 2 effective treatment interventions, in terms of one more criteria: time, cost, error rate
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Order Effects • PRESENTATION ORDER OF ITEMS
• 1-2-3 camel-bat-seal• 1-3-2 camel-seal-bat• 2-3-1 bat-seal-camel• 2-1-3 bat-camel-seal• 3-1-2 seal-camel-bat• 3-2-1 seal-bat-camel
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External Validity
• Generalization -- The degree to which the results of a research study or experiment can be generalized to other groups, settings or situations.
• Problem for SSD
• Solution ?