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Repeatability:
Repeatability is the variation in measurements
observed when one operator repeatedly
measures the same characteristic in the same
place on the same part with the same gauge:
(i.e. variation in measurements under identical
conditions). (See Reproducibility)
A limit within which agreement may be
expected 95% of the time between two test
results obtained in essentially the same conditions and from the same
homogeneous sample of material.
Repeatability is the inherent variation within the measurement instrument
(gauge) and is represented by
repeatability
, which is the standard deviation
of the measurement instrument.
Reproducibility:
Reproducibility is the variation in average
measurements due to factors other than the
machine variation. These factors include, but
are not limited to, operators, different gauges,
temperature, humidity, and part fixturing
technique. (See Repeatability)
Reproducibility is the variation due to the
measurement system.
R & R studies can partition reproducibility into these component parts.
The partitioning can be used to decide where the problem areas are
and improve the measuring system.
Distribution of
Measurements
of the Same
Part
Figure 5. Repeatability
Reproducibility
Operator A
Operator B
Figure 6. Reproducibility
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