Obsolete Units of Measurement: Gone but Not Forgotten On May 20, 2019, a small cylinder of platinum and iridium sitting in a vault outside Paris was let go, kind of. No severance. No farewell lunch. It had defined mass for the entire planet for 130 years, and it found out it was redundant the way most […]
RSS vs. Welch–Satterthwaite: What Your Coverage Factor Is Really Promising Ask ten calibration labs how they combine an uncertainty budget, and nine will say "RSS." Ask the same ten how they pick the coverage factor, and most will say "k = 2, for 95 %." The confidence in that nine out of ten is 90 […]
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 […]
