Hi, I am new to R and AIC scores but what I get from coxme seems wrong. The AIC score increases as p-values decrease. Since lower AIC scores mean better models and lower p-values mean stronger effects or differences then shouldn't they change in the same direction? I found this happens with the data set rats as well as my own data. Below is the output for two models constructed with the rats data set.
>library(survival) >data(rats) > str(rats) 'data.frame': 150 obs. of 4 variables: $ time : int 101 104 104 77 89 88 104 96 82 70 ... $ tumor : int 0 0 0 0 0 1 1 1 0 1 ... $ trt : int 1 1 1 1 1 1 1 1 1 1 ... $ litter: int 1 2 3 4 5 6 7 8 9 10 ... >m1<- coxme(Surv(rats$time, rats$tumor) ~ rats$trt + (1|rats$litter)) >m1 Cox mixed-effects model fit by maximum likelihood Data: rats events, n = 40, 150 Iterations= 10 54 NULL Integrated Penalized Log-likelihood -185.6822 -180.875 -173.7943 Chisq df p AIC BIC Integrated loglik 9.61 2.00 0.0081708 5.61 2.24 Penalized loglik 23.78 13.17 0.0356440 -2.57 -24.82 Model: Surv(rats$time, rats$tumor) ~ rats$trt + (1 | rats$litter) Fixed coefficients coef exp(coef) se(coef) z p rats$trt 0.9124426 2.490398 0.3226733 2.83 0.0047 Random effects Group Variable Std Dev Variance rats.litter Intercept 0.6526484 0.4259500 >m2<- coxme(Surv(rats$time, rats$tumor) ~ rats$litter + (1|rats$trt) ) >m2 Cox mixed-effects model fit by maximum likelihood Data: rats events, n = 40, 150 Iterations= 5 28 NULL Integrated Penalized Log-likelihood -185.6822 -182.3795 -181.3178 Chisq df p AIC BIC Integrated loglik 6.61 2.00 0.036785 2.61 -0.77 Penalized loglik 8.73 1.88 0.011091 4.97 1.79 Model: Surv(rats$time, rats$tumor) ~ rats$litter + (1 | rats$trt) Fixed coefficients coef exp(coef) se(coef) z p rats$litter 0.01425045 1.014352 0.01088983 1.31 0.19 Random effects Group Variable Std Dev Variance rats.trt Intercept 0.6081659 0.3698658 Teresa Iglesias -- View this message in context: http://r.789695.n4.nabble.com/coxme-AIC-score-and-p-value-mismatch-tp2333980p2333980.html Sent from the R help mailing list archive at Nabble.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.