A random variable X has the following probability distribution:
|
X |
0 |
1 |
2 |
|
P(X) |
1/4 |
1/2 |
1/4 |
then, which of the following is correct?
Answer & explanation
Correct answer: option 3
The correct answer is Option (3) → mean = 2 variance **
Given distribution:
X = 0, 1, 2
P(X) = $\frac{1}{4}, \frac{1}{2}, \frac{1}{4}$
Mean:
$E(X)=0\cdot\frac14+1\cdot\frac12+2\cdot\frac14=\frac12+ \frac12 =1$
$E(X^{2})=0^{2}\cdot\frac14+1^{2}\cdot\frac12+2^{2}\cdot\frac14=\frac12+1=\frac32$
Variance:
$V(X)=E(X^{2})-[E(X)]^{2}=\frac32-1=\frac12$
Hence:
Mean $=1$, Variance $=\frac12$
Therefore:
Mean = 2 × Variance
i.e., $1 = 2\cdot\frac12$
Correct option: mean = 2 variance