Dictionary · Statistics
Z-score
A proficiency-testing statistic z = (x − X)/σ_pt comparing a participant result with the assigned value in units of the standard deviation for proficiency assessment; |z| ≤ 2 is conventionally satisfactory.
Related terms
More from Statistics
Gauge R&R
A measurement systems analysis estimating the variation due to the gauge (repeatability) and the operators (reproducibility), commonly expressed as a percentage of total variation or tolerance.
AIAG MSA manual
Metrological compatibility of measurement results
The property of a set of results for a stated measurand such that the absolute difference of any pair is smaller than a chosen multiple of the standard uncertainty of that difference — the VIM's formal test for "do these results agree".
VIM (JCGM 200:2012) 2.47
Measurement trueness
Closeness of agreement between the average of infinitely many replicate measured values and a reference value. Trueness relates inversely to systematic error, not random error.
VIM (JCGM 200:2012) 2.14
Normalized error (En)
The interlaboratory comparison statistic En = (x − X) / √(U²(x) + U²(X)). |En| ≤ 1 indicates agreement within expanded uncertainties; it is the standard scoring for calibration proficiency tests.
ISO 13528:2022
Intermediate precision condition
A condition set spanning the same procedure and location over an extended period, allowing other factors (operator, reference standard, time) to vary.
VIM (JCGM 200:2012) 2.22
Measurement bias
The estimate of a systematic measurement error — typically the difference between the mean of repeated indications and an accepted reference value.
VIM (JCGM 200:2012) 2.18