Figure 2.

Illustration of how FDRs are estimated using a composite target-decoy DB. For each different threshold, one can use the number of decoy hits to estimate the number of wrong PSMs among target hits. See Equation 1.

Cerqueira et al. BMC Genomics 2012 13(Suppl 5):S4   doi:10.1186/1471-2164-13-S5-S4