Model discovery potential versus the number of GRBs in an optimised sub-sample, N_GRB, for 3σ, 4σ, and 5σ in red solid, black dotted, and blue dashed lines. For each sub-sample, only the N_GRB bursts with the best at the given trial factor N_GRB are chosen. The thick lines show the distributions of the likelihood method used in this analysis, the thin lines show the distributions for a simple counting search with fixed quality cuts Λ >  − 5.5, β < 1° (see text).