Question

If a seed is planted, it has a 90% chance of growing into a healthy plant.

If 12 seeds are planted, what is the probability that exactly 3 don't grow?

   

Answer 1

Here probability of success = 0.90

probability of failure = p = 1 - 0.9 = 0.10

Sample size = n = 12

Let X = number of seeds which are not growing.

So X follows binomial distribution with parameters n = 12 and p = 0.10

We want to find the probability that exactly 3 don't grow that is P( X = 3)

Using excel

P(X = 3) = "=BINOMDIST(3,12,0.1,0)" = 0.085233

Note that the general command to find the exact binomial probability in excel is "=BINOMDIST(x, n, p, 0)

So that the probability that exactly 3 don't grow 0.085233