search for: fm1a

All, The code below is for a pseudo dataset of repeated measures on patients where there is also a treatment factor called "drug". Time is treated as categorical. What code is necessary to test for a treatment effect at a single time point, e.g., time = 3? Does the answer matter if the design is a crossover design, i.e, each patient received drug and placebo? Finally, what would

...t > within mixedeffects model > > Hi Spencer, > > Thanks for your reply. > I don't think this answers my question. > > If I understand correctly, your model simply removes the > intercept and thus the intercept in fm1 is the same as the > first time factor in fm1a ... but am I confused as to why the > other coefficient estimates are now different for the time > factor if this is just a re-naming. > The coefficient estimates for the interactions are the same > for fm1 and fm1a, as expected. > > But my question relates to the signifcanc...

Dear All, I'm trying to use waldtest to test poolability (parameter stability) between two logistic regressions. Because I need to use robust standard errors (using sandwich), I cannot use anova. anova has no problems running the test, but waldtest does, indipendently of specifying vcov or not. waldtest does not appear to see that my models are nested. H0 in my case is the the vector of

Hi all, I am running the following model: > glm89.nb <- glm.nb(AvGUD ~ Year*Trt*Micro) where Year has 3 levels, Trt has 2 levels and Micro has 3 levels. However when I run it has a zero inflated negative binomial (as I have lots of zeros) I get the below error message: > Zinb <- zeroinfl(AvGUD ~ Year*Trt*Micro |1, data = AvGUD89, dist = "negbin") Error in optim(fn =