Comment Why do ratings for a single beer change?

Discussion in 'Site' started by Alworth, Dec 28, 2012.

  1. Alworth

    Alworth Aficionado (110) Oregon Feb 28, 2006

    Just looking at the list of Kolsches and saw something odd. One of my favorite local products, Double Mountain, is listed as having a 3.98 rating based on 12 reviews (http://beeradvocate.com/beer/profile/16094/37968). However, when you look at where it's listed among the "top beers for Kolsch" list, it's getting a 3.81 based on 12 reviews.

    What's the story there?

    Thanks--
    Jeff
     
  2. papat444

    papat444 Poobah (1,510) Quebec (Canada) Dec 28, 2006 Verified

    The beers in the "Top" lists show the weighted rank according to this formula:

    How was this list calculated?

    Lists are generated using a Bayesian estimate that pulls data from millions of user reviews (not hand-picked) and normalizes scores based on the number of reviews for each beer. The general statistical formula is:
    weighted rank (WR) = (v ÷ (v+m)) × R + (m ÷ (v+m)) × C

    where:
    R = review average for the beer
    v = number of reviews for the beer
    m = minimum reviews required to be considered (currently 10)
    C = the mean across the list (currently 3.6)
    But enough nerd talk. Let's drink a beer!