Suppose the underlying rate of chronic bronchitis in childre

Suppose the underlying rate of chronic bronchitis in children in the first year of life is 0.05.

3a. What is the probability that among 5 households with 1 newborn infant each, 3 will not develop chronic bronchitis in the first year of life?

3b. What is the probability that among 18 households with 1 newborn infant each, at most 3 will develop chronic bronchitis in the first year of life?

a) probability to develop in 1st year is 0.05

and probability of not having is 0.95

5 households with 1 infant each means that there are total 5 infants

we have to find that 3 not develop the problem

then 5C3*(0.05)^3*(0.95)^2 = 0.0011

B) THERE ARE 18 HOUSEHOLDS AND WITH 1 INFANTS EACH MEANS THAT THERE ARE TOTAL 18 INFANTS

WE HAVE TO FIND THAT AT MOST 3 DEVELOP THE DISEASE MEANS IT WILL COUNT THE CASE FOR 0,1,2,3

P(0)+P(1)+P(2)+P(3) = 18CO*(0.95)^0*(0.05)^18 + 18C1*(0.95)^1*(0.05)^17 + 18C2*(0.95)^2*(0.05)^16+ 18C3*(0.95)^3*(0.05)^15 = 0.0013