Question

The mean number of defective products produced in a factory in one day is 21. What is the probability that in a given day there are exactly 12 defective products?

Answer 1

Let $X=$ the number of the defective products produced: $X\sim Po(\lambda).$

Given $\lambda=21.$

$$P(X=12)=\dfrac{e^{-21}(21)^{12}}{(21)!}=0.011644$$