Posted April 29, 2008 4:51 pm by with 2 comments

Reports are surfacing today that some Google AdWords ads, especially on Google.de (their German TLD), are displaying what may be variables used in determining quality scores: Pscore, mCPC and thresh. The numerical values have been spotted in both sidebar and shaded results:

Various theories have come up to explain the meaning of each variable. mCPC seems to be minimum cost-per-click, but thresh and Pscore have proven more challenging.

As Barry mentions at Search Engine Land, Danny Sullivan found a document (via a Google search for [pscore pagerank], of course) that may shed some light when it says:

Another is pscore which is used for storing the value calculated by PageRank. according to the score. The value of pscore represents the linked …

Search Engine Journal (source of the above English screen caps), on the other hand, references a more generic definition of the term as used in statistics, where it is a commonly used term:

P-score represents minus logarithm of the P-value. P-value measures the probability of achieving the same or better quality of match at a chance, i.e. at random picking the structures from the database. “Quality of match” is a complex characteristics, which accounts for RMSD, number of aligned residues Nalgn, number of gaps Ngaps, number of matched Secondary Structure Elements and the SSE match score. The higher P-score (the lower P-value), the more surprising, or statistically significant, is the match.

I tend to doubt, however, that “Pscore” as used here is the same commonly used variable that had I used in high school statistics.

“Thresh” probably refers to some sort of threshold (unless we’re going to be talking about threshing some wheat…), but without more explanation from Google (which is unlikely to be forthcoming), any postulates (oh, dang, I’m slipping into math jargon!) are pure speculation.