SINGLE CASE METHODOLOGY

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SINGLE CASE METHODOLOGY

• Steven G. Little
• Angeleque Akin-Little
• Walden University, USA

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Overview

• Nature of single case methodology
• General features of single case design
• Types of single case designs
• Data Evaluation Visual Inspection
• Data Evaluation Statistical Evaluation
• Cautions and Considerations

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Definition

• Quasi-experimental research designs involve
  assessing change in a dependent variable on a
  single subject or a small group of subjects.
• Alternative to group designs
• It is NOT a case study. It has much more control
  and rigor than a case study.

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Also called

• Single-Subject Designs
• Single-Participant Designs
• Intrasubject-Replication Designs
• N1 Research
• Intensive Designs
• Repeated Measures Designs
• Clinical Research Model
• Time Series Design

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General Features

• Continuous Assessment - Repeated observations of
  performance over time
• Baseline Assessment - Observing behavior for
  several observation periods before the
  intervention is implemented. Called the A phase.
  Treatment is B phase. The more stable
  performance is during baseline, the better our
  prediction of what future behavior will be like.

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Stable Baseline

• Baseline Projected future performance
• ? ? ? ? ?
• ______________________________________________
• 1 2 3 4 5
• Days

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Increasing Baseline

• Baseline Projected future performance
• ?
• ?
• ? ?
• ?
• ________________________________________
• 1 2 3 4 5
• Days

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Decreasing Baseline

• Baseline Projected future performance
• ?
• ?
• ? ?
• ?
• ________________________________________
• 1 2 3 4 5
• Days

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Variable Baseline

• Baseline Projected future performance
• ?
• ? ? ?
• ?
• ____________________________________________
• 1 2 3 4 5
• Days

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AB Design

• A B
• ? ? ? ? ? ? ?
• ? ?
• 
  ? ?
• ?
  ? ?
• ?
• _________________________________________
• 1 2 3 4 5 6 7 8 9 10 11 12
  13 14 15
• Days

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ABAB Design

• A B A B
• ? ? ? ? ? ?
  ? ?
• ?
  ? ?
• ?
  ?
• ? ?
  ?
• ?
  ? ? ?
• 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
  16 17 18 19 20
• Days

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Problem With ABAB

• A B A B
• ? ? ? ? ? ?
  
• ?
  
• ?
  
• ?
  
• ?
  ? ? ? ? ? ? ? ? ? ?
• 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
  16 17 18 19 20
• Days

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Multiple Baseline
A
B

P1
P2
P2
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Data Evaluation Visual Inspection

• Visual Inspection
• Therapeutic Criterion
• Pattern of Data
• Obvious Effects
• Changes in Magnitude
• Changes in Trend
• Changes in Latency
• Nonoverlapping Data Points

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Changes in Means
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Changes in Level
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Changes in Trend
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Changes in Latency
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NonOverlapping Data Points
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Data Evaluation Statistics

• t and F Tests
• Time-Series Analysis
• Other Tests

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Cautions Considerations

• Blocking Data

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Types of Graphs
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Duration of Phases

• Not specified in advance.
• Collect data and examine it to determine whether
  the data are clear to make predictions.
• If you have trends or variability in the data
  then you may need to extend the phases.
• 3 to 5 days is probably a safe bet for a minimum.

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Contact Information

• Steven G. Little, Ph.D
• Angeleque Akin-Little, Ph.D.
• 152 Shady Acres Rd.
• Tupelo, MS 38804 USA
• 1-662-841-0008
• slittle2_at_waldenu.edu
• aakinlit_at_waldenu.edu