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# An Unbiased Coin is Tossed 4 Times. Find the Mean and Variance of the Number of Heads Obtained. - CBSE (Science) Class 12 - Mathematics

ConceptBernoulli Trials and Binomial Distribution

#### Question

An unbiased coin is tossed 4 times. Find the mean and variance of the number of heads obtained.

#### Solution

$\text{ We have } ,$
$p = \text{ probability of getting a head in a toss } = \frac{1}{2},$
$q = \text{ probability of getting a tail in a toss } = \frac{1}{2}$
$\text{ Let X denote a success of getting a head in a toss . Then } ,$
$\text{ X follows binomial distribution with parameters n = 4 and } p = \frac{1}{2}$
$\therefore \text{ Mean } , E\left( X \right) = np = 4 \times \frac{1}{2} = 2$
$\text{ Also, variance, Var } \left( X \right) = npq = 4 \times \frac{1}{2} \times \frac{1}{2} = 1$

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Solution An Unbiased Coin is Tossed 4 Times. Find the Mean and Variance of the Number of Heads Obtained. Concept: Bernoulli Trials and Binomial Distribution.
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