Foundations

Distinguish exact model values, rounded approximations and estimates from measurements. Declare the rounding rule, preserve information through calculations and unit changes, and interpret resolution, precision, accuracy and the stated uncertainty type without turning a report’s digits into guaranteed bounds.

Choose the physical quantity you want to investigate, specify the point, event or location involved, and explain how a reading relates to that quantity.

Relate indications to standards, then infer measurement results.

Specify how input quantities determine the measurand.

Precision depends on which measurement conditions are held or changed.

A measurand is the quantity intended to be measured, including the relevant system state, components and conditions.

Accuracy describes closeness of a measured value to a true measurand value; trueness concerns agreement of the limiting replicate mean with a reference value; precision concerns agreement among repeated values under specified conditions.

Measurement error is measured value minus reference value.

An influence quantity changes the relation between instrument indication and measurement result without changing the quantity actually measured in a direct measurement.

Verification provides objective evidence that specified requirements are fulfilled.

Under an assigned distribution g_Y for a measurand and a specification interval[T_L,T_U], the conformity probability is∫_(T_L)^(T_U)g_Y(y)dy.

For an upper specification limit T and assigned Y|data∼N(y,u²), accepting only y≤T−zu ensures Pr(Y>T|data)≤1−Φ(z) under that model.

Specific risk concerns an item given its measurement information.

Possible readings differ from a validated interval of measurement.

Instrument properties are specified within a domain of use.

Responding to a target differs from excluding interference.

An undetected input change differs from an interval with no output change.

Time stability differs from short-term repeatability.

A specification limit is not an uncertainty estimate.

More repetitions do not resolve an underspecified measurand.

Relative uncertainty uses a nonzero measured magnitude.

A zero or blank reading can still have uncertainty.

An intended-use target differs from achieved uncertainty.

Within-location changed conditions differ from strict repeatability.

Certification alone does not establish equivalence across procedures.