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  4. A die is tossed thrice. A success is getting 1 or 6 on a toss. The mean and the variance of number of successes

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Q. A die is tossed thrice. A success is getting $1$ or $6$ on a toss. The mean and the variance of number of successes

Probability - Part 2

Solution:

$n=3, p=\frac{2}{6}=\frac{1}{3}$
mean $=n p=3 \times \frac{1}{3}=1$
variance $\sigma^2=n p q=\sqrt{3 \times \frac{1}{3} \times \frac{2}{3}}$
$=3 \times \frac{1}{3} \times \frac{2}{3}$
$\sigma^2=\frac{2}{3}$