RE: Centering (Impact on SE)

From: "KOWALSKI, KENNETH G. [PHR/1825]" <kenneth.g.kowalski@pharmacia.com> Subject: RE: Centering (Impact on SE) Date: Mon, 9 Jul 2001 08:52:08 -0500 Vladimir, Note that in your example the inference (estimate, SE, and t-value) for the slope parameter for age does not change. It is not appropriate to compare the estimate, SE and t-value for the intercept for the centered and w/o centered parameterizations. In the centered case the t-test is testing whether the CL at age 40 = 0, whereas w/o centering the t-test is testing whether the CL at age 0 = 0. Ken