A random variable X has the following probability distribution:
|
X |
-2 |
-1 |
0 |
1 |
2 |
|
P(X) |
0.2 |
0.1 |
0.3 |
0.2 |
0.2 |
The variance of X will be:
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → 1.89
$X:\;-2,-1,0,1,2$
$P(X):\;0.2,0.1,0.3,0.2,0.2$
$E(X)=(-2)(0.2)+(-1)(0.1)+0(0.3)+1(0.2)+2(0.2)$
$E(X)=-0.4-0.1+0+0.2+0.4$
$E(X)=0.1$
$E(X^2)=4(0.2)+1(0.1)+0(0.3)+1(0.2)+4(0.2)$
$E(X^2)=0.8+0.1+0+0.2+0.8$
$E(X^2)=1.9$
$\text{Var}(X)=E(X^2)-\{E(X)\}^2$
$\text{Var}(X)=1.9-(0.1)^2$
$\text{Var}(X)=1.9-0.01$
$\text{Var}(X)=1.89$