🔮Prior

What I believed, and how strongly, before the new data arrived. In Bayesian terms, the probability given to a hypothesis ahead of the evidence. The data turn it into a posterior, which is the prior for next time.

From 🎓 Lecture 14 - Updating beliefs with Bayes, my first session back after Hamburg and the cold. The arithmetic is in 📐 Bayes' rule. The picture that made it stay is in 🎬 Bayes theorem, the geometry of changing beliefs.

Origin: Latin prior, former or earlier, the comparative form that also gives us a priori.

Note to self: a prior is not a prejudice. It is a prejudice that has agreed to be updated.