FAQ06 – How are ratings calculated?

Rating items can be assigned different weights in a rating form. The more the weight, the more influence the rating item has on the overall rating. All of the overall ratings for each entry are calculated first and then averaged. When calculating an overall rating for an entry, each rating item is multiplied by it’s weight, added together and then divided by the sum of all weights to calculate a rating.

For example, if there are two rating items with weights 0.5 and 1.5, both max values 5 and we have a rating entry with values 4 and 3 respectfully, then we calculate the rating as follows

(0.5*5)+(1.5*4)=2.5+6=8.5

This is 8.5/10 score, 4.25/5 stars and 85%.

The plugin supports two types of rating algorithms: average and bayesian. Bayesian averages normalizes rating to be more representative. Here’s the bayesian average formula used by the plugin.

((avg_num_entries*avg_rating)+(this_num_entries*this_rating))/(avg_num_entries+this_num_entries)

avg_num_entries – average number of entries for a post
avg_rating – average overall rating for a post
this_num_entries – number of entries for the current post
this_rating – the overall rating for this post