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From Pat Ferrel <>
Subject Re: How to interpret recommendation strength
Date Thu, 15 Nov 2012 18:07:42 GMT
Oops, I think I found the answer. If so nevermind...

   * This computation is in a technical sense, wrong, since in the domain of "boolean preference
users" where
   * all preference values are 1, this method should only ever return 1.0 or NaN. This isn't
terribly useful
   * however since it means results can't be ranked by preference value (all are 1). So instead
this returns a
   * sum of similarities to any other user in the neighborhood who has also rated the item.

On Nov 15, 2012, at 9:59 AM, Pat Ferrel <> wrote:

Using a boolean data model and log likelihood similarity I get recommendations with strengths.

If I were using preference rating magnitudes the recommendation strength is interpreted as
the likely magnitude that a user would rate the recommendation. Using the boolean model I
get values approaching 2 (this over a quick and small sample so not sure of the real range),
which leads me to the question...

What is the meaning of the strength returned with the recommendation for boolean data?

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