1. The problem statement, all variables and given/known data I'm trying to formulate a formula based on an experiment I did. 2. Relevant equations 3. The attempt at a solution where x_1 = mean (one of 5 mean values) x_i = value of variables (there are 4 of them added together) n = number of variables My problem is, for the left hand side of the formula, I want to show that there are 5 means, so x_1 to x_5 = the right hand side as shown I'm not sure how to show this mathematically. Wonder if anyone might be able to help. Thanks.