Likelihood Ratio Test For Discrete Classes
See Liu, Statistical Genomics: Linkage, Mapping, and QTL Analysis.
pgs 99-100.
"The ratio between the likelihood of Q
taking a value QA,
which maximizes the likelihood, e.g. a maximum likelihood
estimator and the likelihood of Q
under the null hypothesis QN,
e.g. QN = 0.5 is:
L(QA/X) "
L(QN/X)
Likelihood ratio test statistic = G
= 
G has an appropriate X2 distribution.