If X is a random variable representing the number of children that end up having light-colored eyes, then X follows a binomial distribution with success probability p = 0.25 and number of trials n = 5.
The variance of a binomial distribution with these parameters is n p (1 - p), so the variance in this case would be
5 • 0.25 • (1 - 0.25) = 0.9375 ≈ 0.9
