GUM, the Guide to the Expression of Uncertainty in Measurement, defines terms and concepts related to uncertainty. GUM describes methods for uncertainty calculation, and offers guidance for reporting and the documentation of uncertainties in measurement results. Interface knows that understanding GUM and the adherence to good test and measurement practices are essential to minimize uncertainties and ensure reliable measurement results for every application. In addition, reducing uncertainty with regular calibration of testing devices and proper maintenance of the equipment go hand-in-hand with GUM.