find new average if removing one element from current average 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?
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);
For any computer programmers finding this question, the code is very simple.

function removeFromAverage(value, average, samples) {
  if (samples &lt;= 1) {
    return FALSE;
  }
  return ((average - samples) - value) / (samples - 1);
}


value is the value you want to remove from the average, and samples is the number of observations included in the previous average. The if statement is only there in case one sample is used in the previous average, in which case removing that single value would result in zero samples and no calculable average.