X | 1 | 2 | 3 | 4 | 5 | 6 |
---|---|---|---|---|---|---|
P(X) | $\frac{1}{6}$ | $\frac{1}{6}$ | $\frac{1}{6}$ | $\frac{1}{6}$ | $\frac{1}{6}$ | $\frac{1}{6}$ |
अब $\mathrm{E}(\mathrm{X})$ = $\sum \limits_{i=1}^{n} x_{i} p\left(x_{i}\right)$
= 1$ \times \frac{1}{6}$$+2 \times \frac{1}{6}$$+3 \times \frac{1}{6}$$+4 \times \frac{1}{6}$$+5 \times \frac{1}{6}+6$$ \times \frac{1}{6}$$=\frac{21}{6}$
साथ ही $\mathrm{E}\left(\mathrm{X}^{2}\right)$ = $1^{2} \times \frac{1}{6}+2^{2} $$\times \frac{1}{6}+3^{2}$$ \times \frac{1}{6}+4^{2} $$\times \frac{1}{6}+5^{2} $$\times \frac{1}{6}+6^{2} $$\times \frac{1}{6}$$=\frac{91}{6}$
अतः $ \operatorname{Var}(\mathrm{X})$ = $\mathrm{E}\left(\mathrm{X}^{2}\right)$ - $(\mathrm{E}(\mathrm{X}))^{2}$
= $\frac{91}{6}$$-\left(\frac{21}{6}\right)^{2}$ = $\frac{91}{6}-\frac{441}{36}$ = $\frac{35}{12}$
$X$ | $0$ | $1$ | $2$ | $3$ | $4$ | $5$ | $6$ | $7$ |
$P(X)$ | $0$ | $k$ | $2k$ | $2k$ | $3k$ | $k^2$ | $2k^2$ | $7k^2 + k$ |