Assessment of Reliable Change Using 95% Credible Intervals for the Differences in Proportions: A Statistical Analysis for Case-Study Methodology Purpose Case-study methodology studying change is often used in the field of speech-language pathology, but it can be criticized for not being statistically robust. Yet with the heterogeneous nature of many communication disorders, case studies allow clinicians and researchers to closely observe and report on change. Such information is valuable ... Research Note
Research Note  |   June 01, 2015
Assessment of Reliable Change Using 95% Credible Intervals for the Differences in Proportions: A Statistical Analysis for Case-Study Methodology
 
Author Affiliations & Notes
  • Rachael Unicomb
    The University of Newcastle, New South Wales, Australia
  • Kim Colyvas
    The University of Newcastle, New South Wales, Australia
  • Elisabeth Harrison
    Macquarie University, Sydney, New South Wales, Australia
  • Sally Hewat
    The University of Newcastle, New South Wales, Australia
  • Disclosure: The authors have declared that no competing interests existed at the time of publication.
    Disclosure: The authors have declared that no competing interests existed at the time of publication.×
  • Correspondence to Rachael Unicomb: Rachael.unicomb@newcastle.edu.au
  • Editor: Jody Kreiman
    Editor: Jody Kreiman×
  • Associate Editor: Julie Liss
    Associate Editor: Julie Liss×
Article Information
Research Issues, Methods & Evidence-Based Practice / Speech / Research Notes
Research Note   |   June 01, 2015
Assessment of Reliable Change Using 95% Credible Intervals for the Differences in Proportions: A Statistical Analysis for Case-Study Methodology
Journal of Speech, Language, and Hearing Research, June 2015, Vol. 58, 728-739. doi:10.1044/2015_JSLHR-S-14-0158
History: Received June 9, 2014 , Revised January 8, 2015 , Accepted March 28, 2015
 
Journal of Speech, Language, and Hearing Research, June 2015, Vol. 58, 728-739. doi:10.1044/2015_JSLHR-S-14-0158
History: Received June 9, 2014; Revised January 8, 2015; Accepted March 28, 2015
Web of Science® Times Cited: 1

Purpose Case-study methodology studying change is often used in the field of speech-language pathology, but it can be criticized for not being statistically robust. Yet with the heterogeneous nature of many communication disorders, case studies allow clinicians and researchers to closely observe and report on change. Such information is valuable and can further inform large-scale experimental designs. In this research note, a statistical analysis for case-study data is outlined that employs a modification to the Reliable Change Index (Jacobson & Truax, 1991). The relationship between reliable change and clinical significance is discussed. Example data are used to guide the reader through the use and application of this analysis.

Method A method of analysis is detailed that is suitable for assessing change in measures with binary categorical outcomes. The analysis is illustrated using data from one individual, measured before and after treatment for stuttering.

Conclusions The application of this approach to assess change in categorical, binary data has potential application in speech-language pathology. It enables clinicians and researchers to analyze results from case studies for their statistical and clinical significance. This new method addresses a gap in the research design literature, that is, the lack of analysis methods for noncontinuous data (such as counts, rates, proportions of events) that may be used in case-study designs.

Acknowledgments
This research was supported by funds provided by the School of Humanities and Social Science, University of Newcastle, Australia. Such funds are allocated to higher degree research candidates to assist with various administrative aspects of their studies. In this case, Rachel Unicomb was able to access the Statistical Support Service at the University of Newcastle. This research was further supported by funds provided by Speech Pathology Australia by way of a Research-Higher-Degree Student Research Grant. Acknowledgment also goes to Frank Tuyl for his assistance with the Bayesian theory associated with proportions and differences between proportions.
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