Masked Visual Analysis: Minimizing Type I Error in Visually Guided Single-Case Design for Communication Disorders

• Published in: Journal of speech, language, and hearing research Vol. 60; no. 6; pp. 1455 - 1466
• Main Authors: Byun, Tara McAllister, Hitchcock, Elaine R., Ferron, John
• Format: Journal Article
• Language: English
• Published: United States American Speech-Language-Hearing Association 01.06.2017
• Subjects: Biofeedback; Case Studies; Clinical decision making; Communication Disorders; Communication Research; Decision making; Dialects; Error Analysis (Language); Error Correction; Experimenter Characteristics; Hypotheses (Scientific method); Hypothesis Testing; Intervention; Language disorders; Methods; Phase transitions; Research Design; Research Methodology; Research Problems; Researchers; Rhotics; Single subject research; Special education; Speech; Speech disorders; Testing; Tutorial Programs; Ultrasonic imaging; United States
• ISSN: 1092-4388; 1558-9102; 1558-9102
• DOI: 10.1044/2017_JSLHR-S-16-0344

Purpose: Single-case experimental designs are widely used to study interventions for communication disorders. Traditionally, single-case experiments follow a response-guided approach, where design decisions during the study are based on participants' observed patterns of behavior. However, this approach has been criticized for its high rate of Type I error. In masked visual analysis (MVA), response-guided decisions are made by a researcher who is blinded to participants' identities and treatment assignments. MVA also makes it possible to conduct a hypothesis test assessing the significance of treatment effects. Method: This tutorial describes the principles of MVA, including both how experiments can be set up and how results can be used for hypothesis testing. We then report a case study showing how MVA was deployed in a multiple-baseline across-subjects study investigating treatment for residual errors affecting rhotics. Strengths and weaknesses of MVA are discussed. Conclusions: Given their important role in the evidence base that informs clinical decision making, it is critical for single-case experimental studies to be conducted in a way that allows researchers to draw valid inferences. As a method that can increase the rigor of single-case studies while preserving the benefits of a response-guided approach, MVA warrants expanded attention from researchers in communication disorders.