Data Science

Joint Probability

Joint probability is the probability of two or more events occurring simultaneously. Understanding joint probability distributions is fundamental to probabilistic machine learning and Bayesian inference.

Understanding Joint Probability

Joint probability measures the likelihood that two or more events occur simultaneously, expressed mathematically as P(A and B). In machine learning, understanding joint probability distributions is fundamental to building probabilistic models, performing Bayesian inference, and designing generative models that learn how multiple variables relate to each other. Bayesian networks explicitly represent joint probabilities through conditional dependencies, while language models implicitly learn the joint probability distribution over sequences of tokens. Joint probability connects closely to conditional probability through the chain rule, which allows complex distributions to be factored into simpler components. In natural language processing, autoregressive language models decompose the joint probability of a text sequence into a product of conditional probabilities, predicting each token given all previous ones. This concept is also central to hypothesis testing and anomaly detection.

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Data Science

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