On Jun 6, 2012, at 10:59 , lincoln wrote: > > David Winsemius wrote >> >> This is making me think you really have multiple observation on the >> same individuals (and that persons make transitions from one state to >> another as a result of the passage of time. That needs a more complex >> analysis than "simple" logistic regression. You might consider posting >> a more complete description of the study on the SIG Mixed Effects >> mailing list. >> >> -- >> David. >> > > No, I haven't. Individuals are birds marked with an unique alphanumeric code > that gives me information on their gender (sometimes I have this data > sometime I haven't), and their birth date (as a consequence also the age). > There are no multiple observations of the same individual. > > Anyway, I believe I have not been answered to the main question: when using > anova with test "Chisq" between two models, is the difference in deviance > between the two models interpretable as the Chi Square value and the > difference in df interpretable as the df of the Chi square test? > > For instance, given: > >> anova(mod4,update(mod4,~.-cohort),test="Chisq") > Analysis of Deviance Table > > Model 1: site ~ cohort > Model 2: site ~ 1 > Resid. Df Resid. Dev Df Deviance P(>|Chi|) > 1 993 1283.7 > 2 1002 1368.2 -9 -84.554 2.002e-14 *** > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > > Is 84.554 taken as the Chi square value, 9 as the df of the test and the > p-value depending on these two values?
That's the general mechanism, yes. (Whether the chi-square distribution holds after variable selection is a more difficult issue. Frank Harrell might chime in and remind us that there are books on that subject.) -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Email: pd....@cbs.dk Priv: pda...@gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
