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Hyper-geometric distribution problem?
From 20 components, 18 are good, 2 are defective.
If I take 5, the probability all 5 are good is:
r = 18, N-r = 2, n = 5
P(Y = 5) = 0.553.
Now, it takes 2 minutes to install these components if they are good, and 10 minutes to install if they are defective.
What is the mean and variance of the time to install 5 components?
E(X) = 4.5 good components
4.5*2 + .5*10 = 9.5 minutes to install 5 components on average
V(X) = ?
The solution is V(T) =
The solution is 28.755 but I have no idea how!
There's a formula
V(X) = n(r / N)(N-r / N)(N-n / N-1)
So the variance of good components is 0.355. Not sure how to transform this into minutes :(
*It takes 1 minute to install these components if they are good* I typed wrong sorry!
