A question about probability...

[Random Variable]

A bin contains 3 components from supplier A, 4 from supplier B, and 5 from supplier C. If four of the components are randomly selected for testing, what is the probaility that each suppler would have at least one component tesed?

[(3_C_1)*(4_C_1)*(5_C_1)*(9_C_1)] / (12_C_4) is twice the answer. Why is that?

 

is this with or without replacement? Are they selected one at a time, or all at once?

 

[Random Variable]

Originally posted by: FallenHero
is this with or without replacement? Are they selected one at a time, or all at once?

Well, my intrepreation of the question is that there is no replacement and order of selection doesn't matter.