Results from a mixed-effects model run on all genes using the haploid maximum growth rate data in nystatin2.

Coefficients of main effects are the differences in mean maximum growth rate between the single mutant strains and the ancestral strain (difference between MATα and MATa in the case of mating type). Coefficients of interaction terms are the differences in mean maximum growth rate between the double mutant strains and the sum of the two single mutant coefficients added to the ancestral value. Probabilities (p) are the result of an ANOVA between the full model and one lacking that term. The last three columns refer to the type of epistasis present (Fig 1). “Epistasis” indicates a significant departure from an additive model of growth rates, which can be either negative or positive. “Sign” and “Reciprocal sign” refer to cases where the double mutant grows significantly less well than one or both single mutants, respectively.