Expectation-Maximization refers to a two-step, iterative process that is often used when latent or unobserved variables are present underlying a data generation process. It provides the framework used to fit a Gaussian Mixture Model, which has wide application in unsupervised learning contexts. The EM algorithm alternates between the E-step, in which observations are assigned to an underlying distribution with a certain probability, and the M-step, which then maximizes the likelihood of the distributions based on the latest assignments. The algorithm continues iterating between these steps until a state of convergence is achieved, meaning observations are no longer moved around to different distributions, and the parameter estimates for each distribution are optimized for the final assignments.
What is Expectation-Maximization (EM)?
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