Question

Whooping cough (pertussis) is a highly contagious bacterial infection that was a major cause of childhood deaths before the development of vaccines. About 80% of unvaccinated children who are exposed to whooping cough will develop the infection, as opposed to only about 5% of vaccinated children.
A group of 20 children at a nursery school are exposed to whooping cough by playing with an infected childIf all 20 have been vaccinated, what is the mean number of new infections?

Answer 1

A, since n=20 and p=5% if children are vaccinated mean number of new infections =np= 20*0.05=1 p(x<=2) = P(x=0)+P(x=1)