
The tree diagram could be extended indefinitely for any number of coin flips. Thus, there is a 25% of heads occurring twice on two flips of a coin. We can confirm this in the above figure where the probability of heads occurring twice on two flips of a coin can be determined by following the branches that result in an outcome of two heads, and multiplying the probabilities of each branch: In the case of a coin flip, the probability of each outcome is the same, and is just (0.5) n, where n is the number of flips. To determine the probability of the outcome at the end of a tree diagram, multiply the probabilities of each branch leading to the desired final outcome. The probability of either heads or tails occurring on any given flip of a coin is 50%. The flip of a coin is an independent event because the probability of subsequent flips is not dependent upon any previous flips. The example above can be extended to multiple flips of a coin.

This is one way to confirm that the probabilities in your tree diagram are correct. If there are more outcomes, there can be more than 2 branches, but the sum of the probabilities of the outcomes must still be 1 for each event in the tree diagram. In the above case, there are only 2 branches. Note that the sum of the probabilities of the branches of an event must equal 1. The grey circle represents the event of flipping a coin and the branches show that there is a 50% chance of either heads or tails occurring as a result of the coin flip. Below is an example of a basic tree diagram with one event (the flip of a coin) and the probabilities of its two outcomes, heads or tails: The probabilities of the outcomes of an event occurring are displayed along the corresponding branch.Īlthough tree diagrams can be tedious to construct, they are useful for organizing a sequence of events and probabilities in a clear and simple manner. Tree diagrams are made up of nodes that represent events, and branches that connect nodes to outcomes.


In probability and statistics, a tree diagram is a visual representation of a probability space a probability space is comprised of a sample space, event space (set of events/outcomes), and a probability function (assigns probabilities to the events). Home / probability and statistics / inferential statistics / tree diagram Tree diagram
