The GUM in Plain English, Part 7 of 7: Uncertainty Budget: Report It So a Stranger Can Check You Six parts in, we have an expanded uncertainty we can defend: U = 1.71 lbf, k = 2.57, approximately 95 % confidence. This last part covers what most certificates get wrong, reporting it, and then puts […]
The GUM in Plain English, Part 6 of 7: Coverage Factor: Why k = 2 Sometimes Lies Part 5 combined our nine inputs into a combined standard uncertainty of uc = 0.666 lbf. That is one sigma, and by itself, it is too thin to act on. Figure 11. One sigma catches about 68 %. […]
The GUM in Plain English, Part 5 of 7: Combined Standard Uncertainty: The Catch Called Correlation Parts 3 and 4 sized all nine inputs in our 5000 lbf budget: four Type A pieces earned from data, five Type B pieces built from what we already knew. Now you need one number for the result. You […]
The GUM in Plain English, Part 4 of 7: Type B Uncertainty: The Doubt You Already Know Part 3 earned four numbers by repeating measurements: our Type A pieces, led by a 0.58 lbf single-reading repeatability at 3 degrees of freedom. But not all doubt comes from repeating a measurement. Most of it, in a […]
Part 3 of 7: Type A Uncertainty: The Doubt Your Own Data Hands You In Part 2 we wrote the measurement model and named every input in our 5000 lbf budget. Now we start filling in numbers, beginning with the ones we earn ourselves. Figure 4. Four loadings at 5000 lbf: 5000, 5001, 5000, 5001. […]
The GUM in Plain English, Part 2 of 7: Error vs Uncertainty, and the Exhaust Port in Your Model In Part 1 we agreed that a measurement without an uncertainty is an opinion with a decimal point, and we listed where the doubt in a force lab comes from. Before we can size any of […]
Part 1 of 7: Measurement Uncertainty: An Opinion With a Decimal Point Pull any calibration certificate off the shelf, and you will find a line like U = 1.71 lbf, k = 2.57, approximately 95 % confidence. Most of the people who read that line, including some who sign it, could not tell you where […]
