I are analyzing time to event using a Cox model. There is a continuous variable C, and I are conducting a likelihood ratio test comparing the following two models to see if the variable C should be added.
model_a ~ A + B
model_b ~ A + B + C
anova(model_a, model_b, test = "LRT")
In this case, can we call model_a a null model, or is the null model an intercept-only model. There is no intercept-only model in Cox model, so there is no null model?