An Application of Rasch Analysis to the Measurement of Communicative Functioning Purpose: The purposes of this investigation were to examine the construct dimensionality and range of ability effectively measured by 28 assessment items obtained from 3 different patient-reported scales of communicative functioning, and to provide a demonstration of how the Rasch approach to measurement may contribute to the definition of latent ... Research Article
Research Article  |   December 01, 2005
An Application of Rasch Analysis to the Measurement of Communicative Functioning
 
Author Affiliations & Notes
  • Patrick J. Doyle
    Geriatric Research Education & Clinical Center, VA Pittsburgh Healthcare System, Pittsburgh, PA, and University of Pittsburgh
  • William D. Hula
    VA Pittsburgh Healthcare System, Pittsburgh, PA, and University of Pittsburgh
  • Malcolm R. McNeil
    VA Pittsburgh Healthcare System, Pittsburgh, PA, University of Pittsburgh, and University of Pittsburgh Medical Center
  • Joseph M. Mikolic
    VA Pittsburgh Healthcare System, Pittsburgh, PA
  • Christine Matthews
    VA Pittsburgh Healthcare System, Pittsburgh, PA, and University of Pittsburgh
Article Information
Special Populations / Research Issues, Methods & Evidence-Based Practice / International & Global / Language Disorders / Language / Research Articles
Research Article   |   December 01, 2005
An Application of Rasch Analysis to the Measurement of Communicative Functioning
Journal of Speech, Language, and Hearing Research, December 2005, Vol. 48, 1412-1428. doi:10.1044/1092-4388(2005/098)
History: Received September 20, 2004 , Accepted April 4, 2005
 
Journal of Speech, Language, and Hearing Research, December 2005, Vol. 48, 1412-1428. doi:10.1044/1092-4388(2005/098)
History: Received September 20, 2004; Accepted April 4, 2005
Web of Science® Times Cited: 16

Purpose: The purposes of this investigation were to examine the construct dimensionality and range of ability effectively measured by 28 assessment items obtained from 3 different patient-reported scales of communicative functioning, and to provide a demonstration of how the Rasch approach to measurement may contribute to the definition of latent constructs and the development of instruments to measure them.

Method: Item responses obtained from 421 stroke survivors with and without communication disorders were examined using the Rasch partial credit model. The dimensionality of the item pool was evaluated by (a) examining correlations of Rasch person ability scores obtained separately from each of the 3 scales, (b) iteratively excluding items exceeding mean square model fit criteria, and (c) using principal-components analysis of Rasch model residuals. The range of ability effectively measured by the item pool was examined by comparing item difficulty and category threshold calibrations to the distribution of person ability scores and by plotting the modeled standard error of person ability estimates as a function of person ability level.

Results: The results indicate that most assessment items fit a unidimensional measurement model, with the notable exception of items relating to the use of written communication. The results also suggest that the range of ability that could be reliably measured by the current item pool was restricted relative to the range of ability observed in the patient sample.

Conclusions: It is concluded that (a) a mature understanding of communicative functioning as a measurement construct will require further research, (b) patients with stroke-related communication disorders will be better served by the development of instruments measuring a wider range of communicative functioning ability, and (c) the theoretical and methodological tools provided by the Rasch family of measurement models may be productively applied to these efforts.

Acknowledgments
This research was supported by Veterans Administration Rehabilitation Research and Development Project No. C2386R and the Geriatric Research, Education, and Clinical Center of the VA Pittsburgh Healthcare System. Portions of this article were presented to the 2004 Clinical Aphasiology Conference in Park City, UT. The second and fifth authors were supported by a Veterans Health Administration Pre-Doctoral Fellowship during part of the time that they worked on the project. We gratefully acknowledge the assistance and support of Roberta Elman, the Aphasia Center of California, Oakland, CA; Leslie Gonzalez-Rothi and Karen Pingel, Veterans Affairs Medical Center (VAMC) Gainesville, FL; Katherine Ross, Steven Larson, and Alison Belkin, VAMC Phoenix, AZ; Julie Wambaugh, Rosalea Cameron, Aida Martinez, Christina Nessler, and Sandra Wright, VAMC Salt Lake City, UT; and Mary Ann Oakley and Amy Goda, VAMC Pittsburgh, PA.
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