1 raiting subtraction from total weighted rating

Question

This is a 10 star rating.

I have a weighted rating of 8.1 made from 25 users ratings. I want to delete 1 user rating (7.5) that is invalid, how i do direct calculation on this? I don't want to recalculate all 24 ratings that are left.

I tough of this (8.1+7.5)/2 but it doesn't give me the right answer

Any others ideas of subtraction from a weighted rating?

Akimoto · Accepted Answer · 2015-06-06T23:08:28.100

0

When you calculate an average, the formula is :

(rate1 + rate2 + ... + rateN) / number of rates.

So, we have this equation where x is the addition of all rates exept the one you want to substract :

(x + 7.5) / 25 = 8.1

x + 7.5 = 8.1 * 25

x = 8.1 * 25 - 7.5

x = 195

So the answer is 195 / 24 = 8.125

Based on previous, the formula is :

(average * total votes - rate to remove) / total votes - 1

edited Jun 06 '15 at 23:08

answered Jun 06 '15 at 19:21

Akimoto

368
2
11

Yes this works, but i only have the average rating, the number of ratings, and the rating i want to remove, i don't have the sum of all total ratings – PHPCore Jun 06 '15 at 23:02
That is x. In this case 195. – Akimoto Jun 06 '15 at 23:07
Thanks, i figure it out too ^_^ – PHPCore Jun 06 '15 at 23:13

1 raiting subtraction from total weighted rating

1 Answers1