In my system I have users rating objects (e.g. films) from **1 to 5 stars**.
The mean rating clearly tells something about the overall opinion on an object, but I'd like to use a more precise measure of variability.
For example, if the stars are set randomly, if half of the users give 1 and the other half is 5, the average is still 3, so it doesn't tell me the agreement among users.
I'd like a measure that tells me the **inter-subject agreement**, ranging from 1=all users agree, 0=random ratings.

What would be a good and standard measure for this aspect of a set of ratings?


Thanks,
Mulone