# Understanding the IMDb weighted rating function for usage on my own website

I'm trying to implement a review function on my website, but I want it weighed. I checked on IMDb and they have this:

weighted rating $(WR) = (v / (v+m)) R + (m / (v+m)) C$
where:
$R$ = average for the movie (mean) = (Rating)
$v$ = number of votes for the movie = (votes)
$m$ = minimum votes required to be listed in the Top 50 (currently 1000)
$C$ = the mean vote across the whole report (currently 6.8)

Now, I was wondering how I would implement it for my situation. So please help me understand if what I assume here is correct:

$R$ = $\sum$(review of item $X$ * ratingvalue) / (total reviews of item $X$)

$v$ = total reviews of item $X$

$m$ = I have only a few reviews on my site right now, so does it matter what number I provide here? I thought I'd just enter 1

$C$ = which report do they mean by this? Do they mean the average value of a review across all reviews?

Example based on comments below (thanks guys):

Let's say I have two movies with the following ratings: Movie A votes: 8,8,10,5,7,8 Movie B votes: 10

Would that result in the following values for the variables: Movie A total reviews: 6 Movie B total reviews: 1

Movie A sum: 46 Movie B sum: 10

Movie A average: 7,666666667 Movie B average: 10

Thus for movie A the variable values would be: R 7,666666667 v 6 m 0,8 <- with value of variable m I could play based on whether this movie relatively has a lot of reviews C 8

And the rating would be: (WR)=(v/(v+m))R+(m/(v+m))C (WR)=(6/(6+0,8))7,666666667+(0,8/(6+0,8))8 (WR)=7,7

If that's correct: I also tried giving movie A 6*10 and movie B 1*10 but in that case it would make sense to rank movie A higher, which it doesn't with my current formula.

Thanks!

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Think of it as if every item always has $m$ votes which are average. – Thomas Andrews Jul 10 '12 at 13:01

Once you grap the concept, you have quite freedom to prescribe your weights and the "a priori" rating. The important restrictions are: the weights must be in the $(0,1)$ range and sum up to one; the weight of the "a priori" rating should tend to $1$ if the movie has few votes, and to $0$ if it has many.