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USN2ENG
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Homework Statement
What is the probability that among a collection of 20 assemblies we have exactly 2 loose-fits and 1 interference fits?
P(loose-fit) = .1335
P(Interference fit) = .083
Homework Equations
The Attempt at a Solution
I am thinking that I just add the two binomial distributions together.
P(Loose = 2) = (20 choose 2)*.1335^2 * (1-.1335)^18
+
P(Interference = 1) = (20 choose 1)*.083^1 * (1-.083)^19
This comes out to: .25677 + .31998 = .57675
But, I feel like I am missing something. Anyone that can confirm or deny will be much appreciated!
Thanks!