Re: [R] When models and anova(model) disagree...

2011-06-16 Thread Frank Harrell
Without seeing the model I'm not clear on the cause. In general it is not very useful to compute 1 d.f. tests for parameters that represent only part of a meaningful hypothesis. Note that anova.lrm computes Wald statistics, which are subject to the Hauck-Donner effect (which may not be the cause

Re: [R] When models and anova(model) disagree...

2011-06-16 Thread Ben Bolker
Greg Snow imail.org> writes: > The individual tests on coefficients in logistic regression > are generally based on a Wald test statistic. > Unfortunately there is a bit of a paradox possible in this > case where the coefficient is highly > significant, but due to a flattening of the likelihoo

Re: [R] When models and anova(model) disagree...

2011-06-15 Thread Greg Snow
To: r-help@r-project.org Subject: [R] When models and anova(model) disagree... I have a situation where the parameter estimates from lrm identify a binary predictor variable ("X") as clearly non-significant (p>0.3), but the ANOVA of that same model gives X a chi^2-df rank of > 20

[R] When models and anova(model) disagree...

2011-06-15 Thread Rob James
I have a situation where the parameter estimates from lrm identify a binary predictor variable ("X") as clearly non-significant (p>0.3), but the ANOVA of that same model gives X a chi^2-df rank of > 200, and adjudicates X and one interaction of X and a continuous measure as highly significa