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In an effort to expand the pool of scientific evidence available for review, the What Works Clearinghouse (WWC) assembled a panel of national experts in single-case design (SCD) and analysis to draft SCD Standards. In this paper, the panel provides an overview of SCDs, specifies the types of questions that SCDs are designed to answer, and discusses the internal validity of SCDs. The panel then proposes SCD Standards to be implemented by the WWC. The Standards are bifurcated into Design and Evidence Standards (see Figure 1). The Design Standards evaluate the internal validity of the design. Reviewers assign the categories of Meets Standards, Meets Standards with Reservations and Does not Meet Standards to each study based on the Design Standards. Reviewers trained in visual analysis will then apply the Evidence Standards to studies that meet standards (with or without reservations), resulting in the categorization of each outcome variable as demonstrating Strong Evidence, Moderate Evidence, or No Evidence.


Table of Contents

  • Single-Case DesignTechnical Documentation
  • A. Overview of Single-Case Designs
  • B. Causal Questions That SCDs Are Designed To Answer
  • C. Threats to Internal Validity In Single-Case Design
  • D. The Single-Case Design Standards
  • Single-Case Design Standards
  • A. Single-Case Design Characteristics
  • B. Criteria for Designs That Meet Evidence Standards
  • C. Criteria for Demonstrating Evidence Of A Relation Between An Independent Variable And An Outcome Variable
  • D. Visual Analysis of Single-Case Research Results
  • E. Recommendations for Combining Studies
  • F. Effect-Size Estimates for Single-Case Designs
  • References
  • Appendix A—Attrition Diagram
  • Appendix B—Visual Analysis

Document Details

  • Version: 1.0
  • Released: June 2010

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