Directed and valued graph responding to these rules:
- The sum of the values (probabilities) associated with the edges coming from the same vertex gives 1,
- The probability of a path is the product of the probabilities associated with the edges that compose it,
- The value of an edge that goes from vertex S1 to vertex S2 is the conditional probability of the event S2 knowing that the event S1 has already occurred.
Example
Below, we used a probability tree to represent tossing a coin two times.
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