How To Test Baseball Game Prediction System?

[davidr]

I am working on a MLB game prediction system. The system gives a percentage chance that Team A will beat Team B (with pitchers, ballpark, and other factors hopefully taken into account).

My question is how do I determine if my prediction system is accurate? If the Indians are predicted to beat the Tigers 65% of the time when they play on a certain date the actual result will either be an Indians victory or Tiger victory. I would like to know if my 65% was a good estimate.

Let's assume I'm doing this over an entire season where I have percentage chance of victory for each game during that season along with the actual results of those games. How can I test this?

Thanks for you help and if my explanation is unclear ask away and I'll be happy to clarify.

Ultimately, I want to use this system to bet games.

-Dave