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GATE 2010 CS (CS1) – Question 36

Engineering Mathematics · Probability and Statistics · 2 marks · Multiple choice

An assembly is faulty with probability p. A test correctly identifies a faulty or nonfaulty assembly with probability q. What is the probability that the test declares an assembly faulty?

  1. pq+(1−p)(1−q)
  2. (1−q)p
  3. (1−p)q
  4. pq

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Correct answer: (A) pq+(1−p)(1−q)

Explanation

Partition by the true condition. A faulty assembly is declared faulty with probability pq. A nonfaulty assembly is incorrectly declared faulty with probability (1−p)(1−q). These disjoint events sum to pq+(1−p)(1−q), A.

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