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Current Methodological Issues in Single Case Research
David Rindskopf, City University of New York
Rob Horner, University of Oregon
Purposes Inclusion of Single-case Designs in education
research literature. Interpretation of Single-case Research
Visual Analysis Statistical Analysis
Impact of Single-case Research Identification of “Evidence-based Practices” Inclusion of Single-case Research in Meta-
analyses
Toward a Comprehensive Analysis of Single-case Designs
Rob Horner, George Sugai,
Hariharon Swaminathan, Tom Kratochwill, and Joel Levin
Focusing the Discussion We are concerned here only with single-case experimental
designs* ABAB Reversal/withdrawal Designs Multiple Baseline Designs Alternating Treatment Designs• Note: these designs are sometimes conceptualized as within,
combined, and between-series, respectively.
Excluded are AB designs, ABA designs, Interrupted Time Series Case Studies.
The three types of designs can be extended into randomized experiments (Kratochwill & Levin, 2007).
Single Case Research Logic Individual is unit of analysis Dependent Variable
Operationally defined Measured directly Repeated measurement
Independent Variable Measured for implementation fidelity
Replication of effect within an experimental design To control for threats to internal validity
Analysis Needs
Analysis
Questions
Group Designs
Single-case Designs
Experimental Control
(Statistical Significance)
Design
Analysis
RCT, RD
Statistical
MBL, ABAB, etc
Visual Analysis
Effect Size Cohen’s d, r, etc
PND, ?
Social Validity
X
X
X
Visual Analysis Documenting Experimental Control
Three demonstrations of an “effect” at three different points in time. An “effect” is a predicted change in the dependent
variable when the independent variable is actively manipulated.
Visual Analysis includes simultaneous assessment of: Level, Trend, Variability, Immediacy of Effect,
Overlap across Adjacent Phases, Similarity of Data Pattern in Similar Phases.
(Parsonson & Baer, 1978; Kratochwill & Levin, 1992)
Visual Analysis Interpreting experimental control always
involves assessment of data from the whole study (all phases), not just assessment of two adjacent phases. Assessment of an “effect” is done with 2 adjacent
phases. Assessment of experimental control, however,
requires evaluation of all data in all phases.
First Demonstration of Effect
Second Demonstration of Effect
Third Demonstration of Effect
Visual Analysis:
1. Change in Level
2. Change in Trend
3. Change in Variability
4. Immediacy of Effect
5. Overlap
6. Similarity of Data Patterns and Phases
Parsonson & Baer, 1978;
Kratochwill & Levin, 1992
First Demonstration of Effect
Second Demonstration of Effect
Third Demonstration of Effect
Comparison of actual against projected data
(Analysis of Transition States versus Analysis of Steady States)
Statistical Analyses of Single-case Research Documenting Experimental Control/
Statistical Significance: No statistical model currently replicates the
conceptual logic used in visual analysis.
Effect Size Not a variable traditionally addressed in Single-
case Analyses. It needs to be.
Documenting “Evidence-based Practices” via Single-case Research Define “practice” Build professional consensus
Defining a “Practice” A “practice” is a procedure, or set of procedures,
designed for use in a specific context, by individuals with certain skills/features, to produce specific outcomes for specific individuals.
Operationally defined procedures Target population/ Context Implementer Characteristics Defined outcomes
Large practices…small practices
Toward a Professional Consensus Five studies documenting experimental
control Conducted in at least three different locations
by at least three different researchers At least 20 different participants Documenting an effect size of ??
Example of using Single-Case Research to document Evidence-based Practice Functional Communication Training to reduce
problem behavior in school, home and community At least Five Studies
Bird, Dores, Moniz & Robinson (1989) Brown et al., (2000) Carr & Durand (1985) Durand & Carr (1987) Hagopian, Fisher, Sullivan, Acquisto & LeBlanc (1998) Mildon, Moore, & Dixon (2004) Wacker et al., (1990)
At least three settings /scholars Six locations, Research Groups
At least 20 participants 42 different participants document effect
Implications for Single-Case Research Measures
Define assumptions about trajectory Baseline
Document predictable patterns More data points if trend More data points if higher variability
Data points per phase At least 5 points per phase More data when trend and variability is high
Combination of visual and statistical analysis Need for effect size measures in single-case designs
For individual studies For meta-analyses
Summary The inclusion of single-case research findings in a
larger body of education research will require attention to added strategies for interpretation, and added strategies for application
Interpretation Better definition of visual analysis procedures Agreement on effect size index
Application Definition of “evidence-based practices” Protocol for inclusion of single-case research in meta-
analyses.
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