|Total number of votes||1||This value will be seen by users in the problem page.|
|Average value||5||This value will be seen by users in the problem page.|
|Score (lower bound)||1.8261731658956||This value will be used to order problems in highest rated list.|
|Score (upper bound)||5||(not used)|
The score is calculated by Wilson score confidence interval (http://www.evanmiller.org/how-not-to-sort-by-average-rating.html) with 95% of confidence:
where x-bar is ((the average number of stars) - 1) / 4, and the final score is 1 + 4 * (the result of the formula).
The old formula was used until Apr 30, 2012. Thanks to Margus for the correction and logical explanation!