We know a valid LRT should compare nested models. Suppose there are four models:
model1 = gamm4(y ~ x + s(t))
model2 = glmer(y ~ x + t)
model3 = gamm4(y ~ 1 + s(t), random = ~(1|t))
model4 = gam(y ~ x + s(t))
I am not sure they are nested model. Can we compare model1 and model2? And can we compare model3 and model4?
