LOD score ($Z(\theta )={\log }_{10}[L(\theta )/L(1/2)]$)

The LOD score compares the likelihood at recombination fraction $\theta$ with independent assortment:When phenotype likelihood is independent of $\theta$, it can be computed from marker probabilities conditional on phenotype and ascertainment. Positive values support linkage; the observed marker pattern must be specified precisely because affected-only and affected-plus-unaffected observations give different likelihoods.