We make decisions every day based on risk. Some of these decisions are so common that we see them as natural parts of life. Can I see the traffic coming so I can move my car across traffic to safely reach where I am going? Do I need to pack a jacket or umbrella in case of rain later? Many of these decisions are binary (yes or no) and are based on a quick analysis of potential outcomes and their likelihood of positive and negative occurrences for us. With any decision, there is uncertainty in which outcomes and/or occurrence likelihoods are unknown to the decision-maker. How could one know that even though they packed a jacket and umbrella for potential rain, they had not accounted for the bridge to fail and crush them to death? While the likelihood of bridge collapse occurrence was low, the severity of the bridge collapse was high. These potentials are part of the overall uncertainty in life. We have to balance our risk appetite with our desire to live and get things done.
In order for a measurement to be valid, i.e., to have measurement (metrological) traceability, it must be stated with its associated measurement uncertainty. Test or calibration reports with measurement data and its associated uncertainty are information upon which decisions can be made. Is this instrument accurate enough for our use? Can I use this measurement device to calibrate another measurement device? How much product must we scrap to lessen the chance of a failing product being released to the marketplace? How many failing products will we accept in the marketplace? These are all decisions made based on measurements.