Document Detail


Single-case research in neuropsychology: A comparison of five forms of t-test for comparing a case to controls.
MedLine Citation:
PMID:  21843884     Owner:  NLM     Status:  Publisher    
Abstract/OtherAbstract:
Five inferential methods employed in single-case studies to compare a case to controls are examined; all of these make use of a t-distribution. It is shown that three of these ostensibly different methods are in fact strictly equivalent and are not fit for purpose; they are associated with grossly inflated Type I errors (these exceed even the error rate obtained when a case's score is converted to a z score and the latter used as a test statistic). When used as significance tests, the two remaining methods (Crawford and Howell's method and a prediction interval method first used by Barton and colleagues) are also equivalent and achieve control of the Type I error rate (the two methods do differ however in other important aspects). A number of broader issues also arise from the present findings, namely: (a) they underline the value of accompanying significance test results with the effect size for the difference between a case and controls, (b) they suggest that less care is often taken over statistical methods than over other aspects of single-case studies, and (c) they indicate that some neuropsychologists have a distorted conception of the nature of hypothesis testing in single-case research (it is argued that this may stem from a failure to distinguish between group studies and single-case studies).
Authors:
John R Crawford; Paul H Garthwaite
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2011-7-23
Journal Detail:
Title:  Cortex; a journal devoted to the study of the nervous system and behavior     Volume:  -     ISSN:  1973-8102     ISO Abbreviation:  -     Publication Date:  2011 Jul 
Date Detail:
Created Date:  2011-8-16     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0100725     Medline TA:  Cortex     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Copyright Information:
Copyright © 2011 Elsevier Srl. All rights reserved.
Affiliation:
School of Psychology, University of Aberdeen, Aberdeen, UK.
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