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100 units out of each shipment is inspected. Calculate with an

**approximation the probability of finding five or more faulty units.**

__APPROPRIATE__Emphasis from book, not me.

My solution was

A = Bin(100,0.01) ≈ N(1,0.1)

B = Bin(100,0.03) ≈ N(3,1.71)

A+B ≈ N(4,1.71)

P(A+B > 4.5) = 1-P(A+B < 4.5) = /normal table/ = 0.386

Which produced a fairly good answer, but the book also made it clear that they were looking for a poisson approximation. I am not entirely clear on why that is. Anyone?