Dealing with baseline differences: two principles and two dilemmas.

J Jamieson

doi:10.1016/s0167-8760(98)00048-8

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PubMed · 9987061

Dealing with baseline differences: two principles and two dilemmas.

J Jamieson

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Abstract

Two principles are presented that describe directional confounds associated with baseline differences: Principle 1: Change scores are confounded with baseline whenever data are skewed. Principle 2: When baseline differences are real, ANCOVA has a directional bias that magnifies differences in one direction and masks those in the other direction. Both principles involve a directional bias that is related to the direction of baseline difference and the direction of the hypothesized difference in change. Ethical dilemmas arise if decisions (whether or not to transform, whether or not to use ANCOVA) are chosen in order to maximize power by capitalizing on the directional bias and Type 1 error.

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Analysis of Variance Confounding Factors, Epidemiologic Data Interpretation, Statistical Decision Making Ethics, Professional Longitudinal Studies Psychophysiology Research Design Journal Article

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J Jamieson. 1999. Dealing with baseline differences: two principles and two dilemmas.. https://doi.org/10.1016/s0167-8760(98)00048-8

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