TITLE: find new average if removing one element from current average
QUESTION [6 upvotes]: Ok, so say that I have a current rating average: 3.3/5
Now I want to say to remove a rating of 4. How do  I find the new average? Or is this even possible?

REPLY [10 votes]: To fix the problem of thirdender, and put it on a programmatic way.
Substract a value:
average = ((average * nbValues) - value) / (nbValues - 1);

Add a value:
average = average + ((value - average) / nbValues);