Weighted Scores

Hi,

Im working on a scorecard wherein i need to score agents' performance from survey returns received ftom customers. For example: Agent J got 2 surveys with 100% and 90% rating from customers. Agent X got only 1 survey with 100% rating.

So technically, agent X should have a higher score since the average rating is 100% as opposed to agent Js average rating of 95%.

I want to have a type of scoring grid or formula so that the more surveys an agent receives the higher the impact on his score and considering also his average rating. The passing rate by the way is 80% survey rating.

Hope someone can give an idea

Thanks,
Eric