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
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