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Inappropriate use of covariate analysis renders meaningless results

Published online by Cambridge University Press:  02 February 2007

GROVER C. GILMORE
Affiliation:
Department of Psychology and Mandel School of Applied Social Sciences, Case Western Reserve University, Cleveland, Ohio

Extract

In this journal, Anstey et al. (2006) reported the results of a potentially important clinical study on the effect of cataract removal on the cognitive performance of older adults. Unfortunately, because of inappropriate data analyses, some reported results are meaningless. Consequently, the conclusions drawn by the authors regarding the impact of the cataract surgery cannot be considered valid.

Type
LETTERS TO THE EDITOR
Copyright
© 2007 The International Neuropsychological Society

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References

REFERENCES

Anstey, K.J., Lord, S.R., Hennessy, M., Mitchell, P., Mill, K., & Von Sanden, C. (2006). The effect of cataract surgery on neuropsychological test performance: A randomized controlled trial. Journal of the International Neuropsychological Society, 12, 632639.Google Scholar
SPSS Knowledgebase (2001, December 10). Resolution 22133: Repeated measures with constant covariates in GLM. Message archived at: http://support.spss.com/tech/.
Winer, B.J. (1971). Statistical principles in experimental design (2nd ed., p. 797). New York: McGraw-Hill.