i) n=10, p=0.2,

P(X=3)= 10C3x x

= 0.201326592

ii) mean= E(X) = np = 12x0.2= 2.4 or 2 people.

iii)mean = E(X) = np = 25x0.2 = 5 people.

S.D. = (Var(X))^0.5 = (np(1-p))^0.5 = (25x0.2x0.8)^0.5 = 2

iv)Problem

I'm stuck here, I got this far:

1-(P(X=0))=0.95 which goes to

0.05=(P(X=0))

0.05=n(1-p)

0.05=n(0.8)

n=0.0625...?

Where did I go wrong?