Tuesday, March 20, 2007

ROI in SNGs - How Big A Sample Size?

Forums all over the world contain posts asking questions like these:

- After 76 SNGs my ROI is 113%, should I move up levels?
- I have a ROI of 15% over 250 $6.50c turbos - is this good?
- What ROI would a winning player expect at the 16s / 22s / 33s (delete as applicable)?

In case you missed it ROI stands for 'Return on Investment' and is the standard way in which success (or otherwise) is measured for SNGs. What is a 'good' ROI at any particular level depends on many factors including your sample size, level at which you play, number of tables you play at once and situational factors such as the number of winning players at your tables.

The list below is an old set of numbers based on a large sample at Party Poker when still in business in the US (2005 I believe). It is based on someone playing no more than 4 tables at one time.

11s - 25% ROI
20s - 20% ROI
33s - 16% ROI
55s - 13% ROI
109s - 10% ROI
215s - 7% ROI

Things are different here in 2007. Less sites to choose from for multi-tablers, more training available (think PXF / SNG Icons / Cardrunners and the various tools now around) and importantly less losing players around (thinking of the US recreational market being hit by the UIGA and Neteller debarkle). My personal thoughts are to shave 5% off of the first 3 levels and proportionally reduce the rest... there is still a profit to be made, it is just that little bit tougher!

The question I really wanted to look at is about sample size... luckily some of the greatest brains behind the early days of the 2+2 forums have given us a hand here - running simulations of 50,000 games they looked at how often your ROI for a given sample size would reflect your true ability. Here is a summary based on a 10% range:

100 games: ~23%
300 games: ~40%
1000 games: ~66%
2000 games: ~82%

What this tells us (well ok the forum poster mentioned above) is that a 100 game sample has only a 23% chance of being an accurate reflection of ones ability. This makes sense in terms of some of the things we looked at previously here at Plan3t Gong - reverse the outcome of 5 coinflips in 100 games you'll see your ROI quickly halve or double. I feel that the 82% chance of 2000 games reflecting your true ROI also gives us food for thought... that is a lot of games to only be 'pretty sure' you are a winning player.

Will look at various aspects of ROI and confidence intervals in more detail over the coming weeks... for now we know what to think when Mr New-Guy starts boasting about his 50% ROI over 100 games though!!!

Cheers, Mark

1 comment:

MrTynKyn said...

Decrease the % on ROI mark !!! I feel bad :-)