The GATE Grind

GATE 2023 ST – Question 27

Non-parametric Statistics · Rank and Sign Tests · 1 mark · Multiple choice

X₁,…,X_n are iid with density f and median θ. To test θ=θ₀ against θ>θ₀,reject if S>c,where S counts X_i>θ₀. Which statement is true?

  1. Under H₀,the law of S depends on f.
  2. Under H₁,the law of S does not depend on f.
  3. The power function depends on θ.
  4. The power function does not depend on θ.

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Show answer and explanation

Correct answer: (C) The power function depends on θ.

Explanation

Under the continuous null,P(X>θ₀)=1/2,so S∼Binomial(n,1/2) regardless of f. Under an alternative,S∼Binomial(n,p),p=1−F(θ₀),and power is Σ_(j>c) binom(n,j)p^j(1−p)^(n−j). Thus it depends on the alternative distribution and its median parameter,as intended by **C**; the median alone does not specify a unique numerical power without a distributional family.

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