The probability that a person catches a cold during the cold and flu season is 0.62. Assume that 5 people are chosen at random.

Question

A) What is the probability that exactly four of them will catch a cold?
B) What is the probability that three or more of them will catch a cold?
C) On average, how many of these five people would you expect to catch a cold?

Answer 1

prob of cold = .62
prob of not cold = .38

a) prob of 4 of 5 catch cold
= C(5,4) (.62)^4 (.38)

b) prob 3 or more
= prob 3 + prob 4 + prob 5
= C(5,3)(.62)^3 (.38)^2 + C(5,4) (.62)^4 (.38) + C(5,5) .62^5
= ...