Paul H. Garthwaite

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Neuropsychologists often need to estimate the abnormality of an individual patient's test score, or test score discrepancies, when the normative or control sample against which the patient is compared is modest in size. Crawford and Howell [The Clinical Neuropsychologist 12 (1998) 482] and Crawford et al. [Journal of Clinical and Experimental(More)
In neuropsychological single-case studies, a patient is compared with a small control sample. Methods of testing for a deficit on Task X, or a significant difference between Tasks X and Y, either treat the control sample statistics as parameters (using z and zD) or use modified t tests. Monte Carlo simulations demonstrated that if z is used to test for a(More)
Elicitation is a key task for subjectivist Bayesians. While skeptics hold that it cannot (or perhaps should not) be done, in practice it brings statisticians closer to their clients and subjectmatter-expert colleagues. This paper reviews the state-of-the-art, reflecting the experience of statisticians informed by the fruits of a long line of psychological(More)
It is increasingly common for group studies in neuropsychology to report effect sizes. In contrast this is rarely done in single-case studies (at least in those studies that employ a case-controls design). The present paper sets out the advantages of reporting effect sizes, derives suitable effect size indexes for use in single-case studies, and develops(More)
Frequentist methods are available for comparison of a patient's test score (or score difference) to a control or normative sample; these methods also provide a point estimate of the percentage of the population that would obtain a more extreme score (or score difference) and, for some problems, an accompanying interval estimate (i.e., confidence limits) on(More)
Payne and Jones (1957) presented a useful formula for estimating the abnormality of differences between an individual's scores on two tests. Extending earlier work by Sokal and Rohlf (1995) and Crawford and Howell (in press), we developed a modified paired samples t test as an alternative to this formula. Unlike the Payne and Jones formula, the new method(More)
In contrast to the careful consideration given to the issue of what we can infer from dissociations in single-case studies, the more basic question of how we decide whether a dissociation is present has been relatively neglected. Proposals are made for fully operational definitions of a deficit, classical and strong dissociations, and double dissociations.(More)
Corballis [Corballis, M. C. (2009). Comparing a single case with a control sample: Refinements and extensions. Neuropsychologia] offers an interesting position paper on statistical inference in single-case studies. The following points arise: (1) Testing whether we can reject the null hypothesis that a patient's score is an observation from the population(More)
The conventional criteria for a classical dissociation in single-case studies require that a patient be impaired on one task and within normal limits on another. J. R. Crawford and P. H. Garthwaite (2005) proposed an additional criterion, namely, that the patient's (standardized) difference on the two tasks should differ from the distribution of differences(More)
Information on the rarity or abnormality of an individual's test scores (or test score differences) is fundamental in interpreting the results of a neuropsychological assessment. If a standardized battery of tests is administered, the question arises as to what percentage of the healthy population would be expected to exhibit one or more abnormally low test(More)