Ask HN: Please suggest changes/updation to the following rank calculator

Lets assume i have a game X. A group of N number of people play the game and each of them either score POSi or NEGi

I have thought of the following mathematical model , not sure how correct it is, but this is what i came up with. If anyone knows anything better/simpler/standard please mention, also you might suggest changes or point out flaws in the current model. Calculating for users assuming they score Positive scores.

Step1: Calculate the average score of n people `for i in range(1, N): sum = sum + POSi Average = sum/N`

Step2: Calculate the Standard Deviation (SD)

Step3: Calculate the weight of the user as follows say the user has played M matches, his weight W will be Mxabs((sum(POSi)/N1 - (sum(NEGi)/N2))

(where N1 is the number of times he has scored positive scores and N2 the number of times he scored negative result)

Step4: Current Score = (POSi - SD)xW

Step5: His New Rating = Old Rating + Current Score

Maybe it sounds naive, but this is what i could think of, suggestions are invited.

Thanks!