Question

 Determine the binomial distribution where mean is 9 and standard deviation is `3/2` Also, find the probability of obtaining at most one success. 

Answer 1

E(X) = 9 = nP               .........(1)

`therefore 9/4 = npq `

`therefore 9/4 = 9 xx q`

`therefore q = 1/4            therefore p = 3/4`

`9 = 3/4n rArr n = 12`

`P(X = x)=^12C_x (3/4)^x(1/4)^(12-x)`     ...........(0 ≤ X ≤ )

P(X ≤ 1) = P (X = 0) + P (X = 1)

`= ^""12C_0 (3/4)^circ (1/4)^12 + ^12 C_1 (3/4)^1 (1/4)^11`

`= (1/4)^12 + 12 xx 3/4 xx (1/4)^11`

`= (1/4)^12 (1+36)`

`= 37/4^12 = 37/2^24 = 0.0000022054