Here's the question you clicked on:
radh
A manufacturer produces a large number of microwaves. From past experience, the manufacturer knows that approximately 1.5% of all its microwaves are defective. Consumer Reports randomly selects 20 of these microwaves for testing. You want to determine the probability that no more than one of these microwaves is defective.
What is the probability that at most two of the microwaves are defective?
It's just binomial distribution, no?
Yeah, but how would I get it with x<=2. I know how to do x=2, but not x<=2.
\[ \Pr(X\leq 2) = \Pr(X=0, X=1, X=2) = \Pr(X =0) + \Pr(X = 1) +\Pr(X = 2) \]
Ah, alright. Thanks. I get it now.
They're mutually exclusive events. They can't have both exactly 2 and exactly 1 defective microwave.