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GATE 2022 ST – Question 42

Estimation · Confidence Intervals · 2 marks · Multiple choice

One observation has density 2x/θ² on 0<x<θ. Using pivot X/θ,which interval is an 80% confidence interval for θ when x=10? Limits are rounded to three decimals.

  1. (10.541,31.623)
  2. (10.987,31.126)
  3. (11.345,30.524)
  4. (11.267,30.542)

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Correct answer: (A) (10.541,31.623)

Explanation

The pivot U=X/θ has CDF u² on (0,1). Its .1 and .9 quantiles are √.1 and √.9. Thus P(√.1<U<√.9)=.8. Inverting gives (x/√.9,x/√.1)=(10.541,31.623). **A**.

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