29
% Contribution (R&R) should be less than 30%. If the %
Contribution (R&R) is greater then 30%, work should be
refocused on reducing measurement variability before any
further analysis is performed.
If there is a specified tolerance for the characteristic being measured, then
use the following four steps to determine the process to tolerance (P/T)
ratios.
Calculate the process to tolerance ratio (P/T) for repeatability using
the following equation.
P
/
T
=
Z
x
USL
LSL
x 100
Repeatability
0
Repeatability
Determine if the P/T (Repeatability) is acceptable using the following
guideline:
If P/T (Repeatability) is small (i.e. < 5% or less), then it is acceptable.
This will help insure attainment of acceptance of % Contribution
(R&R). If the P/T (Repeatability) is greater than 5%, then the
measurement system may not be adequate for this
application.
Calculate the P/T for the measurement instrument using the following
equation:
P
/
T
=
Z
x
USL
LSL
x 100
where
=
0
R&R
R&R
Repeatability
2
Reproducibility
2
Determine if the measurement instrument P/T is acceptable using
the following guideline:
% Contribution (R&R) should be less than 30%. If the %
Contribution (R&R) is greater then 30%, work should be
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