Table 2.

Contingency table for the phenotypic values of strictly beneficial alleles. The categories of ɛ classified by the four conditions are analogous to the possible outcomes of tossing a coin twice, and allow us to compute the overall probability of negative and of positive ɛ, giving , where B_tot = B_a + B_u.

ɛ	−	−	+	+
condition	λi > θi	λi < θi	λi > θi	λi < θi
	λj > θj	λi < θj	λj < θj	λj > θj
region (i , j)	(Ba, Ba)	(Bu, Bu)	(Ba, Bu)	(Bu, Ba)
p(condition)