Hello! I have a question regarding measurement uncertainties. This is not a homework problem. Let's say that I want to measure some quantity, and I want to measure it multiple times using multiple identical but separate instruments. That is, -First measurement taken using equipment 'A' -Second measurement taken using equipment 'B' -Third measurement taken using equipment 'C' 'A', 'B', 'C' are all the same type of equipment and somehow it is known that they each have the same 'X' % uncertainty in their individual measurements. Once I have the set of measurements I can look at them individually with their 'X' % uncertainty, or I can look at them as a group. How do I propagate the 'X' % uncertainty in each individual measurement into a group uncertainty? Of course you could take the results and find a mean value and associated standard deviation, but how does the 'X' % uncertainty come into the picture?