Likelihood Ratio Test

library(MASS)
data(Melanoma)
attach(Melanoma)
mod1 = lm(time ~ age + thickness)
mod2 = lm(time ~ age + thickness + ulcer)
logLik(mod1)

## 'log Lik.' -1716.784 (df=4)

logLik(mod2)

## 'log Lik.' -1713.282 (df=5)

t1 = as.numeric(logLik(mod1))
t2 = as.numeric(logLik(mod2))
teststat = 2*(t2-t1)
teststat

## [1] 7.003376