Question

If a seed is planted, it has a 75% chance of growing into a healthy plant.

If 6 seeds are planted, what is the probability that exactly 4 don't grow?

Answer 1

It is binomial:

p= 0.75 = 75%

1-p = 0.25 = 25%

N = 10

k=7

"seven successes in 10 trials"

(10 choose 7) (0.75)^7 ( 0.25)^3 =

(10*9*8 / 3*2) * (0.75)^7 ( 0.25)^3 =

(5*3*8) (0.75)^7 ( 0.25)^3

120 (0.75)^7 ( 0.25)^3

= 0.25028228759765625

or just over 25%

Explanation: