The GATE Grind

GATE 2020 ST – Question 15

Probability · Random Variables and Transforms · 1 mark · Multiple choice

X has MGF $M_X(t)=1/6+e^t/3+e^{2t}/3+e^{3t}/6$. Find P(X≤2).

  1. 1/3
  2. 1/6
  3. 1/2
  4. 5/6

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Correct answer: (D) 5/6

Explanation

The MGF identifies masses1/6,1/3,1/3,1/6 at0,1,2,3 respectively. Adding the first three gives1/6+1/3+1/3=5/6, D. The remaining1/6 is the probability at3.

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