The expectation value (E-Value) is the number of sequences in a database that are expected to have P-Scores equal to or better than what was observed by chance. Low E-Values represent better matches (less likely to be false positives) than high E-Values. Because the P-Score represents the probability of the n out of f fragments matching by chance, and if it is assumed that all sequences in the database are independent, the E-Value of a sequence-fragment set association is the P-Score multiplied by the number of sequences in the database.
If N is the number of proteoforms considered during a search, the E-Value currently reported by the software is:
