The standard deviation of the number of tails in three tosses of a coin is:

$\frac{\sqrt{3}}{2}$

The correct answer is Option (4) → $\frac{\sqrt{3}}{2}$

Let X = number of tails in 3 tosses of a fair coin

X follows Binomial distribution: n = 3, p = 0.5

Variance of binomial: σ² = n p (1 − p) = 3 × 0.5 × 0.5 = 0.75

Standard deviation: σ = √0.75 ≈ 0.866