The random variable x can take values 0, 1, 2, 3, Given that P(x=0)=P(x-1)=P and P(x-2)=P(x-3) such that $E(x^2)=2E(x)$, then value of 'P' is :
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → $\frac{3}{8}$
Given,
$P(x=0)=P(x-1)=P$
$P(x-2)=P(x-3)$
$E(x^2)=2E(x)$
Since the total probability must be 1,
$p+p+q+=1$
$⇒p+q=\frac{1}{2}$ ....(1)
$E(x)=0.p+1.p+2.q+3.q=p+5q=\frac{1}{2}+4q$
$E(x^2)=0^2.p+1^2.p+2^2.q+3^2.q=p+13q=\frac{1}{2}+12q$
and,
$E(x)=E(x^2)$
$\frac{1}{2}+4q=\frac{1}{2}+12q$
$q=\frac{1}{8}$
$⇒p=\frac{3}{8}$