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GATE 2026 ST – Question 56

Estimation · Point Estimation and Consistency · 2 marks · Multiple select

An iid sample n≥2 has Laplace density e^(−|x−μ|)/2,μ∈ℝ. Let μ̂ be an MLE and X̄ the sample mean. Which hold?

  1. The MLE always exists and equals X̄.
  2. The MLE may fail to exist.
  3. The MLE always exists but may not be unique.
  4. The MLE consistently estimates μ.

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Correct answer: (C) The MLE always exists but may not be unique.; (D) The MLE consistently estimates μ.

Explanation

Maximizing likelihood minimizes Σ|x_i−μ|. A minimizer is any sample median: unique for odd n (almost surely), and the entire interval between the two middle order statistics for even n. Thus it always exists but can be nonunique. Both middle sample quantiles converge to the unique population median μ; any selection between them is consistent. **C,D**.

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