1) Beer Ratings: These are the ratings that you see on the beer page, wish list, etc. These are now calculated at a PURE average. They are no longer weighted against other beers. To get a rating, a beer must have 10 or more ratings.
2) Brewery Ratings: These are the ratings that appear on the brewery page. They are a pure average rating of all beers
3) Top Rated Breweries: The list shows the top breweries, based on our weighted average formula (below), which effectively rates all breweries against each other and gives weight to their beers with higher rating count. A brewery must have at least 1,000 ratings and at least 5 beers on their beer page to qualify for this list.
4) Top Beers / Weighted: These are the beers you see on the "Top Rated" page on the web and in-app. These ratings, are still done by our old system (Bayesian Average - http://en.wikipedia.org/wiki/Bayesian_average). You must have 150 ratings to qualify for this list. PLEASE NOTE: These ratings for Top Beers are not shown on a Beer page - HOWEVER a beer's weighted rating can be found in-app by selecting "Everyone". The official formula:
$avg_num_ratings // Average number of ratings in all beers $avg_rating // Average rating for all beers $this_num_rating // Number of votes for the beer in question $this_rating // Pure Average Rating for the beer in Question $bayesian_rating = ( ($avg_num_ratings * $avg_rating) + ($this_num_rating * this_rating) ) / ($avg_num_ratings + $this_num_rating);
Ratings are still calculated once per day. Every time you make a rating on Untappd - it will be stored, but the average rating is refreshed on a daily basis.
Frequently Asked Questions about Ratings
When you rate beer on a check-in all previous ratings are averaged up and applied to beer. You can rate as a many times as you want - but you only get 1 rating per beer per user. This cuts down on rating abuse. If you delete a checkin that you rated, that rating will be removed.
You cannot rate a beer a 0. If you do - it's the same as not rating the beer. By not rating a beer, it doesn't count toward it's total. It doesn't mean a 0 rating.
How often does the list of Top Rated _____ refresh? About every 24 hours - but there are factors that could increase or decrease that timeframe.
Ratings on Brewery and Beer will update every 24-48 hours depending on the number of check-ins to the beer or brewery.
If you have any questions - let us know by opening a discussion at http://untpd.it/newticket.