PGMDR, and another SNP, rs3743078 in the CHRNA3 gene, without a main effect, was detected in three of the five best interaction models, power calculation with Quanto for detecting interaction between two genetic loci, g and h, was performed for three sets of parameters: (1) in the absence of main effects for g and h and in the presence of an interactive effect between g and h (assuming Rg = 1, Rh = 1, and Rgh = 1.5, 2.0, 2.5, and 3.0); (2) in the absence of a main effect for g only, and in the presence of a main effect for h as well as an interactive effect between g and h (assuming Rg = 1, Rh = 1.25, and Rgh = 1.5, 2.0, 2.5, and 3.0); and (3) in the presence of main effects for g and h, as well as an interactive effect between g and h (assuming Rg = 1.25, Rh = 1.25, and Rgh = 1.5, 2.0, 2.5, and 3.0) under the dominant model for both loci and the MAF for gene h = 0.30. The required sample sizes were 717, 754, and 795 for Rgh = 2.0, 436, 464, and 496 for Rgh =
