Question 848324
X~ Binomial(n=5, p=.84)

a)  

P[X=4] = (5 choose 4)*(.84)^4*(.16)^1 = .3983

b) Use complement since we're talking about 1 calculation as opposed to 4. I say 1 because we already calculated P[X=4].

So we calculate P[X=5] = (5 choose 5) *(.84)^5 *(.16)^0 = .4182

then P[X<4] = 1-P[X>=4] = 1-(P[X=4] + P[X=5]) = 1-(.3983+.4182) = .1835

c) mean of binomial : np =  5*.84 = 4.2

sd of binomial : sqrt(npq) = sqrt(4.2*.16) = .82