3.1 What is a Beta Binomial model for ?

• It is a model we use when we want to look at something with a proportion.

• Examples of use: The proportion of people that use public transit, the proportion of trains that are delayed, the proportion of people that prefer cats to dogs, and so on.

• The Beta-Binomial model provides the tools we need to study the proportion of interest,\(\pi\), in each of these settings.