The discussion I had many times at work with the numpties on the hangar floor was some thing like "this gauge is out!!" Me, "How did you arrive at that conclusion??". Numpty " Its 5 PSI higher than that gauge".... "Hmmm, maybe its correct, and the other gauge is out, or they could both be within tolerance..". Numpty "????? How can that be?? " ..... "Well, they are both allowed to be 4.8 PSI either side of the true reading, so one could be a little high, and the other a little low. So really, they are both OK. Bring them to the shop and I can test them. "
Numpty turns up at the Cal lab a week later with a gauge still in the packet " Can you test this??".... Sure, where are the other 2?? ". N "I threw them out cos I couldnt trust them and got a new one." After a quick test on the .1% standard gauge.. " Well there you are, this gauge is good, its 2PSI low over the range, good to go. Here is the cal sticker and the certificate will be on file". N " but its out!!??!! " ....
"No, its in tolerance take it and go away"