Errors and Uncertainty in Measuring

9. With a little practice you can measure the groove width with an uncertainty as little as 0.002 inches or 0.05 mm (i.e. it could be wrong by at most 0.02 inches or 0.05 mm). In tests for conformity the manufacturer is given the benefit of all of that uncertainty. This is done by subtracting 0.02 inches or 0.05 mm from all the measurements noted in Section 7, namely Wav, Wmax and Wvar, to give “adjusted” values of these quantities. We call them AWav, AWmax and AWvar; it is these which are used in all tests for conformity.