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GATE 2023 ST – Question 46

Probability · Random Variables and Transforms · 2 marks · Multiple choice

X has CDF 0 for x<−1,(x+1)/4 for −1≤x<0,(x+3)/4 for 0≤x<1,and 1 for x≥1. Which holds?

  1. lim P(−1/2+1/n<X<−1/n)=5/8
  2. lim P(−1/2−1/n<X<1/n)=5/8
  3. lim P(X=1/n)=1/2
  4. P(X=0)=1/3

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Correct answer: (B) lim P(−1/2−1/n<X<1/n)=5/8

Explanation

The CDF has a jump of 1/2 at zero and density 1/4 elsewhere on (−1,1). The limiting interval in B includes that atom and length 1/2 of continuous density,giving 1/2+(1/2)(1/4)=5/8. A excludes the atom and tends to 1/8. C is zero for n>1,and D’s atom is 1/2. **B**.

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