Voting/Rating Algorithm

Hey guys,

Just looking for some advice on developing a voting/rating algorithm.

What is the most effective way to develop this?

Right now, I am using minimalistic/very simple algorithm, I have two columns: Num_Votes and Vote_Total, and the rating is Num_Votes/Vote_Total.

Problem is, it can be easily skewed if their are a low number of votes (1 vote of 5 will boost them to a 5 star rating).

Thanks guys!

 

$total_stars_to_show = 5;

$total_voters   = 16; #assumed
$total_ratings  = 47; #assumed

$average = ($total_ratings / $total_voters) * $total_stars_to_show;

PHP:

Now it also depends upton the width of the image you use tod display a star. For example width per star image is 10 pixels, then you will create a <span of $average * 10, which will be in code as:

$positive = (int)($average * 10);

PHP:

and populating the two spans first for positive feedback and remaining the negative, thus:

$total_width = 10 * $total_stars_to_show;
$negative = $tota_width - $positive;

PHP:

$positive:$negative
-------------------
+++++++:---------
-------------------

CSS

Assuming height of image too is 10 pixels.

.Cpositive {
    background-color:blue;
    background-image:url("positive_star.gif");
    height:10px;
}
.Cnegative {
    background-color:gray;
    background-image:url("negative_star.gif");
    background-position:top right;
    height:10px;
}

HTML:

PHP

echo "<span class=\"Cpositive\" style=\"width:{$positive}px\">
echo "<span class=\"Cnegative\" style=\"width:{$negative}px\">

PHP:

I hope it helps, if this is what you required.

 

so does it work better.
for example. i had a video rated 4 times and it had 4 stars, and a video that hadnt had any ratings and i rated it a 5 star and it became the top rated video.. but it really wasnt due to 1 vote and the other video had 4 votes..

i want to fix that problem... any way?

 

It is assumed that single vote might have rating 1-5.. Sorr for late reply.

 

You need to remember voter ip address and do not allow him to vote again and again.

 

Simply you need to use Bayes’ Theorem.
See How to implement an accurate rating system

 

Thanks neo, you always help me.

 

This is exactly what I've been looking for too! Thanks man!

 

That's a really good post - I should look into it for improving my own website!

A simple alternative (but not as good) is to show the number of ratings along with the average rating, then the user will see which ratings are more reliable.