[jay_shark]

You can translate your ROI to win-rate .

i.e., If your win-rate is x % (written in decimals) and your ROI is y% then we solve for :

(2*x-1.05)/1.05 = y Or x =[1.05y +1.05]/2

so if Y=15% , then x is about 60% .

In laymen's terms :

Roi = [2* win-rate - buy-in ]/ (buy-in)

Win-rate= [buy-in* Roi + buy-in ]/2

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Or we may make the assumption that your standard deviation is ~ 1 which applies to a wide range of win-rates .

So if after 500 sng's , your sample roi is 15% , then our confidence interval at two standard deviations from the mean becomes :

0.15 +-2*1/sqrt(500) which implies that our true win rate(z=2) is anywhere between [0.15 - 0.089, 0.15 + 0.089] or [6%, 23.9%]

After 2000 games , it is [ 10.5% , 19.47%]

Hope that helps