Chapter 4 Flashcards
An approach to the estimation of uncertainty based on a dissection of a method or process from the ground up. A fishbone (cause and effect) diagram is often used in this process
Bottom-up model
A diagram used in uncertainty estimation procedures that involves diagramming and associating individual contributors to uncertainty of a measurement process and how they are related to each other
Cause-and-effect diagram (fishbone diagram)
The sum of the squares of the uncertainty contributors, typically in an uncertainty budget form
Combined standard uncertainty
The multiplier used to calculate an expanded uncertainty; typically values of 2 or 3 are used, roughly corresponding to the 95% and 99% confidence intervals
Coverage factor (k)
The product of the combined uncertainty (u) multiplied by the coverage factor k
Expanded uncertainty (U)
An internationally accepted guide that describes in detail how to estimate the uncertainty of a measurement
Guide to the Expression of Uncertainty in Measurement (GUM)
A committee formed representing several international metrology organizations, IUPAC and ISO
Joint Committee for Guides in Metrology (JCGM)
A sample or set of samples collected in such a way that there is an equal probability of any one sample being selected
Random sample
How many decimal places can be read off the display with the understanding that there is uncertainty associated with this last place
Readability of a balance
A form of distribution in which there is equal probability across a range
Rectangular distribution
The uncertainty contribution from a single factor, expressed as the equivalent of a standard deviation
Standard uncertainty (u)
A weight of a controlled substance that defines the severity of a crime or penalty
Threshold weight
An approach to the estimation of uncertainty in which individual contributors are captured using techniques such as control charting
Top-down model
A form of distribution in which there is a higher probability of a value occurring in the middle of the range than at the extremes
Triangular distribution
A contribution to uncertainty that can be described by a normal distribution
Type A contribution
