Greater observed frequency is associated with functional indicators. (All) refers to all alternative splices identified in the ESTs; (conserved) refers to the subset of alternative splices detected as being conserved in mouse ESTs; (mRNA verified) refers to the subset of alternative splices also identified in the GenBank mRNA collection. Thez-score is interconvertible with the binomial probabilityP(‖Y‖ ≥ k‖ n, p), which was calculated for a threshold frequency of p = 0.05 (see Methods). (A) A significant difference between thez-score distribution for all alternative splices and the distribution for conserved alternative splices is seen, which indicates that conserved events tend to occur at higher frequencies. (B) A significant difference between the overall z-score distribution and the distribution for mRNA verified alternative splices is also seen.