It's meant to be as a joint probability. I'm a little confused by your response though, I thought Poisson was mostly used for when you're only given a mean/average success rate and need to solve using it? I'm assuming here you mean to find this rate and then apply it?
In the case of an...
Homework Statement
Suppose that X=time to failure for a component has an exponential distribution with lambda =.25. Suppose that 9 of the components are selected and their failure times noted. Compute the probability that 3 of the components fail between times 1 and 2, and 4 of the components...