# Presentation: 300818

## 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)

- First Demonstration of Effect

- Second Demonstration of Effect

- Third Demonstration of Effect

- First Demonstration of Effect

- Second Demonstration of Effect

- Third Demonstration of Effect

## 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.