Machine-translated by Google. Questions are authored in English.
Top

Discussion

The distributions of X under \(H_{0}\) and \(H_{1}\) are given by :

\(x\)1234
\(H_{0}\)0.250.250.250.25
\(H_{1}\)0.170.170.170.32

The most powerful test at level \(\alpha = 0.05\) is given by :

  • A.reject \(H_{0}\) if X = 4
  • B.reject \(H_{0}\) with probability 0.25 if X = 4
  • C.reject \(H_{0}\) with probability 0.2 if X = 4
  • D.reject \(H_{0}\) with probability 0.32 if X = 4

Answer: C

The most powerful test rejects \(H_{0}\) with probability 0.2 if X = 4.

By the Neyman-Pearson lemma, reject where \(P_{1}(x)/P_{0}(x)\) is largest. The ratio is \(0.17/0.25 = 0.68\) at \(x = 1, 2, 3\) and \(0.32/0.25 = 1.28\) at \(x = 4\), so \(x = 4\) comes first. Rejecting at \(x = 4\) always would give size 0.25, too large, so randomise there:

\[ 0.25\gamma = 0.05 \Rightarrow \gamma = 0.2 \]

The non-randomised test in A has size 0.25, not 0.05. Rejecting with probability 0.25 or 0.32 gives sizes 0.0625 and 0.08, also above the level.

No comment is present. Be the first to comment.
Loading…

Post your comment

Please log in or register to post a comment.