Kowalski C J, Schneiderman E D, Willis S M
Department of Biologic and Materials Sciences, University of Michigan, Ann Arbor 48109.
Int J Biomed Comput. 1994 Nov-Dec;37(3):189-94. doi: 10.1016/0020-7101(94)90117-1.
In many biomedical research contexts, treatment effects are estimated from studies based on subjects who have been recruited because of high (low) measurements of a response variable, e.g., high blood pressure or low scores on a stress test. In this situation, simple change scores will overestimate the treatment effect; and the use of the paired t-test may find significant change due not to the treatment per se but, rather, due to regression towards the mean. A PC program implementing a procedure for adjusting the observed change for the regression effect in simple pre-test-post-test experiments is described, illustrated, and made available to interested readers. The method is due to Mee and Chua (Am Stat, 45 (1991) 39-42) and may be considered as an alternative to the paired t-test which separates the effect of the treatment from the so-called regression effect.
