I am running a Cox-proportional hazards model and using AIC for model selection (I am doing reverse selection, but manually rather than using a program). In the output for AIC, both a "without covariates" and a "with covariates" value are shown. What is the difference between these two values, and which should I be using for model selection?
Without covariates - this is the null model (essentially the information conveyed by the mean alone)
With covariates - this includes any independent variables. If you are doing some sort of model selection, you should notice a change in the "with covariates" value as the number of independent variables included changes.
ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.