Question

Thirty-three percent of workers in a city are college graduates. If you randomly select 20 workers...

(A) what is the probability that five or six of them are college graduates?

(b) what is the probability that more than 2 are college graduates ?


Can someone please help I am struggling

Answer 1

Prob(graduate) = .33
prob(not grad) = .67

prob(probability that five or six of the 20 are grads)
= C(20,5)(.33)^5 (.67)^15 + C(20,6) (.33)^6 (.67)^14
= ..... you do the button pushing stuff

prob(of 20 that more than 2 are grads)
= prob(3 are grads) + prob(4 are grads) + ...+ prob(20 are grads)
too much work, so

prob(of 20 that more than 2 are grads)
= 1 - (prob(0 grads) + prob(1 is a grad) + prob( 2 are grads)
this way you only have 3 calculations
= .....