Question

If $X$ is a random poisson variate such that $E\left(X^2\right)=6$, then $E\left(X\right)=$

• A. $-3$
• B. $2$
• C. $-3\&2$
• D. $-2$

Answer 1

Answer: (B)

$2$

Variance = $E\left(X^2\right)-E[X{]}^2$
Mean = Variance for P.D.
Let mean = $m$
Therefore
$m=$ $6-m\ast m$
Hence
$m=2$