Consider two discrete random variables indicating the length of a product produced by two machines (machine A and machine B). The normal length should be $450$ mm, but the length of the product varies for each machine with the following probabilities.
My question is which machine is more reliable?
I have calculated the expected value of the product length for each machine, and both are equal to $450$ mm.
Since the expected value equals the the normal length, do we have to check the probability $\Pr(X=450)$ at each machine?