Differing curvature measures in NonlinearRegress
- To: mathgroup at smc.vnet.net
- Subject: [mg90253] Differing curvature measures in NonlinearRegress
- From: "Gy. Csanády" <csanady at helmholtz-muenchen.de>
- Date: Thu, 3 Jul 2008 06:13:21 -0400 (EDT)
Dear Madam Dear Sir; I have a question related to the NonlinearRegress-procedure where Mathematica calculates the FitCurvatureTable. In this table the values of =93Max Intrinsic=94, =93Max Parameter-Effects=94 and of =9395% confidence region=94 are given. For a statistical comparison the intrinsic and parametric curvature should be compared to the curvature over the 95% confidence region, which is 1/(2*Sqrt(F(p,n-p,a)), where F is the corresponding F- distribution at a significance level a, with p the number of parameters and n the number of data points (see e.g. Ratkowsky (1983) Nonlinear regression modeling). Mathematica seems to give only the radius of curvature (1/(Sqrt(F(p,n- p,a)) which cannot be compared directly with the other curvature measures listed in the FitCurvatureTable. A clarification would be appreciated. With best regards Gy=F6rgy Csan=E1dy