[Spamassassin Wiki] Trivial Update of "HitFrequencies" by DanielQuinlan

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The following page has been changed by DanielQuinlan:
http://wiki.apache.org/spamassassin/HitFrequencies

The comment on the change is:
edit conflict

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  A ''good'' rule has a very extreme S/O (near as possible to 1.0 or 0.0) and a high percentage of hits in the correct category.  In other words,  RCVD_IN_OPM_HTTP is a very good rule in the example above, because it hits 5.2028% of all spam mails without hitting any ham at all (no false positives).
  
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- S/O stands for "spam% / overall%", in other words, the proportion of the total hits that were spam messages.  As such, it is equivalent to Bayesian probability, or Positive Predictive Value in bioinformatics or medicine.
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- ---- /!\ '''Edit conflict - your version:''' ----
  S/O stands for "spam / overall" for which the formula is "spam% / (ham% + spam%)", in other words, the proportion of the total hits that were spam messages.  As such, it is equivalent to Bayesian probability, or Positive Predictive Value in bioinformatics or medicine.
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  == Measuring Rule Overlap ==