Antwort: RE: COVARIATE MODELS

From FERDINAND.ROMBOUT.FR@bayer-ag.de Thu Jun 12 07:01:33 1997 Subject: Antwort: RE: COVARIATE MODELS It is all a matter of sensitivity. In example A one tries to estimate a slope and intercept. But since one, as has been mentioned, has no weight lets say smaller than 30, a small variation in slope can cause a big variation in intercept, therefore making the model more difficult to predict and sometimes instable. The result will be often bigger errors in the estimated parameters compared with method B were the intercept is more or less in the middle of the weight data, making a stable and more precise prediction of slope and intercept possible. This means we should not center around 70, but should center about the average of our covariate data in the dataset, ie average weight, height, albumin etc. F. Rombout Clinical Pharmacokinetics Department of clinical pharmacology Bayer AG Wuppertal, Germany