Mixture responsibilities and EM

Problem

At a data point xx, two Gaussian-mixture components have prior weights 0.40.4 and 0.60.6 and component densities p(xz=1)=0.3p(x\mid z=1)=0.3 and p(xz=2)=0.1p(x\mid z=2)=0.1. Compute posterior responsibilities and state the E- and M-step roles.

Reveal answer or reference solution

The unnormalized weights are 0.120.12 and 0.060.06, so the responsibilities are 23\frac{2}{3} and 13\frac{1}{3}. The E-step computes responsibilities; the M-step updates parameters using those expected assignments.

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