Bayes' Theorem — Probability in 60 Seconds #Shorts

Added: 2026-05-05

[00:00:00]A positive test result doesn't always mean you're sick. Sometimes the math works against your intuition. This is BA theorem. The logic of updating your beliefs as new, often messy evidence arrives. Imagine a rare disease affecting one in a thousand people. You test positive. How scared should you be?

[00:00:20]Most guess 99% because the test is accurate. But we have to look at the entire population. If you test everyone, most positives are actually false alarms simply because the disease is so rare.

[00:00:34]Bay theorem balances the prior probability of having the disease against the test reliability. The formula connects the probability of being sick given a test to the probability of testing positive given you're sick. The result, your actual risk might be below 10% despite that 99% accurate test. So when you see new evidence, don't just react. Calculate how much your belief should actually change.