We’ve improved the calculation of the average rating for the sources grouped by platform in our All-in-One Reviews app 
Previously, the arithmetic mean was calculated as (source_1 + source_2 + … + source_n) / n.
Now, the weighted average is calculated as (source_1 * number_of_reviews_1 + source_2 * number_of_reviews_2 + … + source_n * number_of_reviews_n) / (number_of_reviews_1 + number_of_reviews_2 + … + number_of_reviews_n).