Estimation of statistical parameters for score distribution of gapped alignments. (A) Obtained alignment score distribution of unrelated hits; COMA scores are fitted to the extreme value distribution considering only the hits with the score of at least 63 (the dashed line). (B) Estimation of the scale statistical parameter λ and (C) the localization statistical parameter μ . Standard errors of the estimates are shown with error bars. The dashed line denotes the level at which the fluctuation of the statistical parameters becomes small.