Likelihood-ratio test statistic
= Likelihood-ratio test statistic
For nested null and alternative parameter spaces, the likelihood-ratio test statistic is
$$
-2\log\Lambda
=2\left\{\sup_{\theta\in\Theta_1}\ell(\theta)
-\sup_{\theta\in\Theta_0}\ell(\theta)\right\}.
$$
Under the regularity conditions of <Wilks theorem>, its null limit is a <chi-squared distribution> whose degrees of freedom equal the difference in model dimensions.