How to calculate probability when your world is split in two

Bayes' Theorem - Example: A disjoint union · 8:32 · Video: Dr. Trefor Bazett · Watch at the source

In short: Most real-world probabilities aren't simple coin flips; they involve categories. This video breaks down how to use Bayes' Theorem to navigate a sample space divided into distinct groups, like vaccinated versus unvaccinated populations.

The lesson centers on the "two bucket" problem, a foundational way to visualize how probability shifts when an outcome can belong to one of two mutually exclusive categories. By understanding this disjoint union, you can solve complex problems by calculating the likelihood of an event occurring within specific subsets of a larger group.

While the video uses buckets as a visual aid, the logic applies to any binary division in data. It introduces the formal calculation for P(B1|A), which determines the probability of being in category B1 given that event A has occurred, by weighing the likelihoods and prior probabilities of both possible categories.

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