If we two discrete random variables they show the length of a product which are produced by two machines. The normal length is 450 mm but there are some deviations. I have calculated the expected value for each machine, and both are equal to 450 mm. And it is asked which machine is more reliable. Since the expected value is at each machine the normal length 450 mm, do we have to check the probability $P(X=450)$ at each machine?
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