If the probability distribution of X is :
Then variance is equal to : |
$\frac{14}{3}$ $\frac{14}{9}$ $\frac{14}{11}$ $\frac{70}{3}$ |
$\frac{14}{9}$ |
The correct answer is Option (2) → $\frac{14}{9}$ The expected Mean Value is, $E(X)=∑X.P(X)$ $=2×\frac{1}{15}+3×\frac{2}{15}+4×\frac{3}{15}+5×\frac{4}{15}+6×\frac{5}{15}$ $=\frac{70}{15}$ $E(X^2)=∑X^2.P(X)$ $=2^2×\frac{1}{15}+3^2×\frac{2}{15}+4^2×\frac{3}{15}+5^2×\frac{4}{15}+6^2×\frac{5}{15}$ $=\frac{350}{15}$ Variance, $σ^2=E(X^2)-[E(X)]^2$ $=\frac{350}{15}-\frac{4900}{225}$ $=\frac{5250-4900}{225}=\frac{350}{225}=\frac{14}{9}$ |