My colleague, Shannon Appelcline, has been working on a game rating system for RPGnet. This has resulted in real-world application of the principles for designing rating systems which we've previously discussed in our Collective Choice articles. Shannon's newest article, Ratings, Who Do You Trust? offers a look at weighting ratings based on reliability.
On the RPGnet Gaming Index we've put this all together to form a tree of weighted ratings that answer the question, who do you trust?
Here's how we measured each type of trust, and what we did about it:
Volume of Ratings for an Item. Introduce a bayesian weight to offset the variability of items with low-volume ratings.
Volume of Ratings by a User. Give each user a weight based on his volume of contribution which is applied to his ratings.
Depth of Content by a User. Give each rating a weight based on the depth of thought implicit in the rating which is applied to that rating.
These all get put together to create our final ratings for the Gaming Index, with each user's individual rating for an item getting multiplied by its user weight and its content weight, and then all of that averaged with the other user ratings and the bayesian weight too. The result is in no way intuitive, but users don't really need to understand the back end of a rating system. Conversely we hope it's accurate, or at least more accurate than would otherwise be true given the relatively low volume of ratings we've collected thus far.
Here are some of Shannon's earlier discussions about the design behind the new "user content" based RPGnet Gaming Index:
- Encouraging User Creativity - A look at the "XP" system which has helped to incentivize the creation of the database at the heart of the ratings.
- Managing User Creativity, Part Two - An examination of the nuts and bolts of RPGnet's Gaming Index database.
Related articles from this blog:
2005-12: Systems for Collective Choice 2005-12: Collective Choice: Rating Systems 2006-01: Collective Choice: Competitive Ranking Systems 2006-08: Using 5-Star Rating Systems 2007-01: Experimenting with Ratings
Related articles from Shannon Appelcline's Trials, Triumphs & Trivialities: