#### Question

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

#### Solution

\[\text{ We have } , \]

\[p = \text{ probability of getting a head in a toss } = \frac{1}{2}, \]

\[q = \text{ probability of getting a tail in a toss } = \frac{1}{2}\]

\[\text{ Let X denote a success of getting a head in a toss . Then } , \]

\[\text{ X follows binomial distribution with parameters n = 4 and } p = \frac{1}{2}\]

\[ \therefore \text{ Mean } , E\left( X \right) = np = 4 \times \frac{1}{2} = 2\]

\[\text{ Also, variance, Var } \left( X \right) = npq = 4 \times \frac{1}{2} \times \frac{1}{2} = 1\]

Is there an error in this question or solution?

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.