= Genetic-study ascertainment
= Ascertainment in a genetic study
{synonym}
<Ascertainment in a genetic study> specifies how individuals or families enter a genetic study. If $A$ is the event of inclusion, then $P(X\mid A)=P(X)P(A\mid X)/P(A)$. Selection on disease <phenotype> can change an unconditional <pedigree likelihood>. When comparing <genetic marker> <probabilities> conditional on a specified disease pattern, selection depending only on that pattern cancels from the linkage <likelihood ratio>.
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