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How does BIC choose k in GMM?

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Answer

  • BIC = -2 log L + p log n where p = number of free parameters, n = dataset size.
  • Lower is better.
  • Balances fit (log L) against complexity (p log n).
  • For GMM, p grows with k and covariance type.
  • Standard practice: fit GMM at k = 1..KmaxK_{\mathrm{max}}, plot BIC vs k, pick the minimum (or the elbow).
  • More reliable than AIC for clustering.
Check yourself — multiple choice
  • Higher BIC is better
  • BIC = -2 log L + p log n; fit at k=1..KmaxK_{\mathrm{max}}, pick minimum; balances fit vs complexity → standard for GMM k selection
  • Same as elbow
  • Random

BIC in GMM: minimize -2 log L + p log n over k.

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