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Unit 2: Statistical Decision Theory

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Maximum Likelihood estimation finds
(i) Prior probabilities
(ii) Parameters that maximize data likelihood
(iii) Decision boundaries
(iv) Cluster centroids

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Answer: (ii) Parameters that maximize data likelihood

Explanation:

Maximum Likelihood Estimation (MLE):

θ^MLE=arg⁡max⁡θL(θ)=arg⁡max⁡θp(D∣θ)=arg⁡max⁡θ∏ip(xi∣θ)\hat{\theta}_{MLE} = \arg\max_{\theta} L(\theta) = \arg\max_{\theta} p(D|\theta) = \arg\max_{\theta} \prod_i p(x_i|\theta)

  • Finds parameter values that make observed data most probable under assumed model.
  • Example: For Gaussian, MLE gives sample mean μ^=xˉ\hat{\mu}= \bar{x} and sample variance (biased) σ^2=1n∑(xi−xˉ)2\hat{\sigma}^2 = \frac1n\sum(x_i-\bar{x})^2.
  • Contrast MAP: arg⁡max⁡p(θ∣D)∝p(D∣θ)p(θ)\arg\max p(\theta|D) \propto p(D|\theta)p(\theta) includes prior.

It does NOT find priors (i), decision boundaries (iii) directly, or cluster centroids (iv) — those are consequences after estimation.

So (ii) is correct.

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