More on Correct Definition of the Experimental Unit An Extension of Max and Onghena (1999) Letter to the Editor
Letter to the Editor  |   October 01, 2000
More on Correct Definition of the Experimental Unit
 
Author Affiliations & Notes
  • Carla J. Johnson
    Department of Speech-Language Pathology University of Toronto Toronto, Ontario, Canada
Article Information
School-Based Settings / Research Issues, Methods & Evidence-Based Practice / Language Disorders / Social Communication & Pragmatics Disorders / Speech / Letters to the Editor
Letter to the Editor   |   October 01, 2000
More on Correct Definition of the Experimental Unit
Journal of Speech, Language, and Hearing Research, October 2000, Vol. 43, 1290-1291. doi:10.1044/jslhr.4305.1290
History: Received January 14, 2000 , Accepted May 31, 2000
 
Journal of Speech, Language, and Hearing Research, October 2000, Vol. 43, 1290-1291. doi:10.1044/jslhr.4305.1290
History: Received January 14, 2000; Accepted May 31, 2000
More on Correct Definition of the Experimental Unit: An Extension of Max and Onghena (1999) 
Max and Onghena (1999)  are to be commended for their excellent tutorial, in which they remind speech, language, and hearing researchers to consider carefully the key assumptions underlying commonly used statistical analyses. Violations of these critical assumptions may result in inappropriate statistical analyses and, perhaps, erroneous substantive conclusions. Max and Onghena highlight two specific issues that are sometimes neglected by researchers in our field: the sphericity assumption in repeated measures designs and the definition of the experimental unit in both completely randomized and repeated measures designs. Regarding the latter issue, they discuss one situation in which researchers have sometimes chosen the incorrect unit of analysis, thereby violating the important assumption of independence of observations. Specifically, when data are collected from subjects over multiple trials, researchers have sometimes erroneously treated trials, rather than subjects, as the unit of analysis.
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