PC PROGRAM IMPLEMENTING AN ALTERNATIVE TO THE PAIRED T-TEST WHICH ADJUSTS FOR REGRESSION TO THE MEAN

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 score s 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 effec t 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 alternat ive to the paired t-test which separates the effect of the treatment f rom the so-called regression effect.