Likelihood Ratio Test:
The likelihood ratio test is aimed at testing a simple null hypothesis against a simple alternative hypothesis. (See Hypothesis for an explanation of "simple hypothesis").
The likelihood ratio test is based on the likelihood ratio r as the test statistic:
where X is the observed data (sample), is the conditional probability of X provided the hypothesis H is true, H0 is the null hypothesis, H1 is the alternative hypothesis. See also Likelihood function.