Journal of the International Neuropsychological Society



LETTER TO THE EDITOR

Use of covariates in randomized controlled trials


GERARD J.P.  VAN BREUKELEN  a1 c1 and KOENE R.A.  VAN DIJK  a2 a3
a1 Department of Methodology and Statistics, Maastricht University, The Netherlands
a2 Department of Neurocognition, Maastricht, The Netherlands
a3 Department of Psychiatry and Neuropsychology, Maastricht, The Netherlands

Article author query
van breukelen gj   [PubMed][Google Scholar] 
van dijk kr   [PubMed][Google Scholar] 

A recent discussion in this journal illustrates some recurrent misunderstandings about the role of covariates in randomized controlled trials (RCTs). This letter aims at clarifying this role and at pointing out a pitfall in SPSS repeated measures ANOVA. We hope that our commentary will contribute to a further improvement in the use of advanced statistics in neuropsychology.

(Received March 9 2007)
(Revised April 5 2007)
(Accepted April 5 2007)


Correspondence:
c1 Correspondence and reprint requests to: Gerard J.P. Van Breukelen, Department of Methodology & Statistics, Maastricht University, P.O. Box 616, 6200 MD, Maastricht, The Netherlands. E-mail: gerard.vbreukelen@stat.unimaas.nl