Spam Filter Batting Average
John Graham-Cumming proposed this uniform measure of spam-filter effectiveness in his November 16, 2004 article entitled 'Understanding Spam Filter Accuracy'.
let fp = false positive percentage let fn = false negative percentage batting average hitrate = (1 - (fn / 100)) batting average strikerate = (fp / 100) batting average = "hitrate/strikerate"
so if you have an FP% of 0.03%, and an FN% of 2.47%, the batting average is
(1 - (2.47 / 100)) "/" (0.03 / 100) = .9753/.0003
That's actually the correct batting average for SpamAssassin 3.0.0's scoreset 3, measured against the validation corpus when we released it.