Probability Trees

In this section we’re going to see how to use probability trees to visualise conditional probabilities.

Watch the video and then answer the questions below.

Ten-minute video

You can also view this video on YouTube


Key Points

We can represent a sequence of decisions as a decision tree. If we attach probabilities to each choice, we get a probability tree.

Each choice is labeled with it’s conditional probability, i.e. “given you’ve got here in the tree, what is the chance you’ll pick this choice”.

To find the probability of a particular path through the decision tree (i.e. that a specific sequence of decisions is made), you multiply along the branches.

Because paths are mutually exclusive, you can add their probabilities to find their joint probability.


Summary

In this section we saw probability trees.

In the next section we look at the Law of Total Probability.