Figure 2

Illustrating the single genetic marker versus multi-marker local SEMs used in the definition of the LEO.NB score. The single genetic marker is denoted by M in (a) and the multiple genetic markers are denoted by $M_A^{(i)}$ and $M_B^{(j)}$ in (b) and (c). By definition, LEO.NB(A˃B) = log₁₀{P (model 1)}/{max_i>1{P (model i)}} for a candidate A → B edge orientation, where the models in the definition are pictured in (a) for single marker LEO.NB scores, and in (b) for multiple marker LEO.NB scores. In (b) we show the orthomarker models used for the LEO.NB.OCA marker aggregation method. The hidden confounder C in model 4 is the causal parent of both A and B, i.e. A ← C → B. The simulation studies in Additional File 1 show that the LEO.NB.OCA score can be significantly more powerful than the LEO.NB.CPA score.