Weighted Mean

* WR=Weighted Rating (The new rating)
* R=Average Rating (arithmetic mean) so far
* V=Number of ratings given
* M=Minimum number of ratings needed
* C=Arithmetic mean rating across the whole site

(5 + 5 + 4)/3 = 4.67 (rounded)

rating  / weight
5 / 2 (since it was given 2 times)
5 / 2
4 / 1

(sum[(rate * weight)])/(sum of weights)
(5 * 2) + (5 * 2) + (4 * 1) / (2 + 2 + 1)
(24)/(5)
= 4.8

select sum(response*ct*ct)/sum(ct*ct) from
( select response, count(response) as ct from your_table group by response) data

select sum(response*ct*ct)/sum(ct*ct) from
( select response, count(response) as ct from your_table group by response) data