Probability as bookkeeping

Probability is careful accounting for what you don't know. Sample spaces, distributions, Bayes' rule as a picture, expectation and covariance, the Gaussian in one and many dimensions, and the two limit theorems stated correctly.

55 min

After this lesson you can

  • Define sample spaces, events, random variables, pmfs and pdfs, and say why a density can exceed 1
  • Move between joint, marginal and conditional distributions with the sum and product rules
  • Derive Bayes' rule and apply it to a base-rate problem
  • Compute expectations, variances and covariances, and read a covariance matrix as an ellipse
  • State the law of large numbers and the central limit theorem with their conditions

In this lesson

  1. Outcomes, events and the rules of the game
  2. Random variables and their distributions
  3. Joint, marginal and conditional
  4. Bayes’ rule, as a picture
  5. Expectation, variance, covariance
  6. The Gaussian
  7. Two limit theorems, stated carefully
  8. In code

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