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GATE 2020 ST – Question 26

Probability · Random Variables and Transforms · 1 mark · Numerical answer

X has characteristic function φ(t)=sin(t)cos(t)/t for t≠0 and φ(0)=1. Find P(|X|≤3/2) (two decimals).

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Correct answer: 0.75 to 0.75

Explanation

Use sin t cos t=(1/2)sin2t, giving φ(t)=sin2t/(2t), the characteristic function of Uniform[−2,2]. The event spans length3 inside a total interval length4, so probability=3/4=0.75.

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