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How accurate are the E-value statistics?

April 26, 2017accurate e-value statistics

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How accurate are the E-value statistics?

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In mpiBLAST 1.3 or later, they are exact for all supported search types. In versions 1.2.1 and earlier, e-values for blastn were loosely approximated using a linear equation. For blastp, blastx, tblastn, and tblastx they were inaccurate in versions 1.2.1 and earlier. Note that by “exact” we mean exactly the same as those generated by NCBI-BLAST with the traditional search engine. As of 2009, NCBI is still refining the e-value calculations in their blast implementation.