Find the probability that exactly two babies were born deaf.

Question

According to a recent article the average number of babies born with significant hearing loss (deafness) is approximately

two per 1,000 babies in a healthy baby nursery. The number climbs to an average of 30 per 1,000 babies in an intensive care

nursery.

Suppose that 1,000 babies from healthy baby nurseries were randomly surveyed.

Answer 1

This would be a binomial distribution, 2 possibilities, either deaf or not. Let's call probability a baby is deaf p, then not deaf would be 1-p. Of course p = 1/1000

There are ₁₀₀C₃ combinations of choosing 2 from 1000. So P = ₁₀₀C₂ * p² * (1-p)⁹⁹⁸

Providing answers will do you little good. You need to understand the meaning of each element of the equation. You might want to consider hiring a tutor.

Cheers,

Patrick