Probability is defined as a measure of how often a particular event will take place if the experiment occurs repeatedly. Probability ranges from zero to one. Zero indicates that the event is impossible, and one indicates that the event definitely will occur. The higher the probability the more likely it is that the event will transpire. There’s probability and conditional probability. This article focuses on sports analytics conditional probability.
Probability relates to all past experiments, or occurrences, of that sequence. However, it is often useful to narrow down the situation to include only those with specific criteria. Instead of simply looking at the probability of a baseball team winning a game, you may want to know the probability of the New York Yankees winning when Aaron Judge hits a home run. In this case, you would use conditional probability. Conditional probability is a measure of the probability of an event happening given that another event has occurred. Conditional probability allows us to add extra conditions to the scenario we want to explore.
Conditional probabilities are very helpful as they allow us to include additional information or assumptions into the calculation. They provide information pertinent to a more specific event, rather than simply a general event. However, you must be careful when determining which information to use or the conditional probability may show a relationship between two events that are completely independent, meaning they have no effect on each other. You might look at the probability of the Seattle Mariners winning a game when Edwin Diaz is in the bullpen. The probability will be inaccurate, as having Edwin Diaz in the bullpen does not mean that he necessarily pitched in the game and if he did not pitch he would have no effect on whether or not the Mariners won.
Analysts can use conditional probability in a myriad of ways. They can look at how any player or event can affect the outcome of a game or the likelihood of a player scoring in a given situation. This analysis gives them the capability to rank the effectiveness each player has in a given situation. This information can be used when looking at possible trades or draftees. Which of the available players would have the greatest likelihood of scoring for their new team? This information helps determine which players would be the best choices to improve the weak spots in their team’s roster.
Coaches can use conditional probability to help determine their line-up for any specific game. A baseball coach can use conditional probability to determine the likelihood of each his players scoring a run when facing the scheduled pitcher. It also helps in deciding when to put a designated hitter or designated runner into the game in order to increase their probability of scoring in a given scenario and improving the team’s chances of winning the game.
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