A cautionary note on the use of the Analysis of Covariance (ANCOVA) in classification designs with and without within-subject factors.

ABSTRACT: A number of statistical textbooks recommend using an analysis of covariance (ANCOVA) to control for the effects of extraneous factors that might influence the dependent measure of interest. However, it is not generally recognized that serious problems of interpretation can arise when the design contains comparisons of participants sampled from different populations (classification designs). Designs that include a comparison of younger and older adults, or a comparison of musicians and non-musicians are examples of classification designs. In such cases, estimates of differences among groups can be contaminated by differences in the covariate population means across groups. A second problem of interpretation will arise if the experimenter fails to center the covariate measures (subtracting t

SUBMITTER: Schneider BA 

PROVIDER: S-EPMC4404726 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature