Differences between revisions 3 and 4
 ⇤ ← Revision 3 as of 2004-12-01 20:26:12 → Size: 1099 Editor: JustinMason Comment: ← Revision 4 as of 2009-09-20 23:16:57 → ⇥ Size: 1103 Editor: localhost Comment: converted to 1.6 markup Deletions are marked like this. Additions are marked like this. Line 3: Line 3: [http://jgc.org/ John Graham-Cumming] proposed this uniform measure of spam-filter effectiveness in [http://www.jgc.org/antispam/11162004-baafcd719ec31936296c1fb3d74d2cbd.pdf his November 16, 2004 article entitled 'Understanding Spam Filter Accuracy']. [[http://jgc.org/|John Graham-Cumming]] proposed this uniform measure of spam-filter effectiveness in [[http://www.jgc.org/antispam/11162004-baafcd719ec31936296c1fb3d74d2cbd.pdf|his November 16, 2004 article entitled 'Understanding Spam Filter Accuracy']].

# 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'.

Essentially, it's a reformatting of the FalsePositive percentage and FalseNegative percentage, as 'spam hit rate / ham strike rate'. This can be computed from FP%/FN% as follows:

```  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.

See also MeasuringAccuracy for other schemes used, or FpFnPercentages for the main one we use in SpamAssassin.

BattingAverage (last edited 2009-09-20 23:16:57 by localhost)