How does ESPN calculate the probability of a team winning a game? ESPN has a probability winning percentage in which what team has more of a probability of winning the game. Like team A is up a certain amount of points and time remaining they’ll have a certain percentage chance of winning the game. How does ESPN calculate that?
 A: I have worked sports prediction and I can say you that they are calculated by algorithmic machines models as opposed to static mathematical formulas. Every sport has its own way of calculating the winning probability i.e. the algorithm that you use in football is most likely very different form the one you use in basketball because the key variables that influence wins in one sport is different from that of another. Moreover, the algorithms used by one company say ESPN will be different from that used by another say Fox Sports, so practically there is no and there wont be one correct answer. It is simply what ever the model the person calculating the probability thinks best describes the historical data.
In individual sports like tennis it is relatively simpler as you only need to account for the players form, history and form of the surface (clay, hard court, grass etc) but team sports, it get high complex as you have the account for the strengths and weakness of each individual player and winning combinations.
In this basketball win probability prediction competition which was funded by Google, you can see how different people build different prediction models on the same data.
By the way if you are able to come up with a good algorithm for even one sport, you can make millions in the sports betting industry.
Here is a another practical working algorithm:
