28
where “Z
0
” in the equation is used to assume a certain % confidence
in the spread of the data. A typical value of 5.15 is used to assure
a 99% confidence. See Table 3 on the next page.
% Confidence
Z
0
90
3.29
95
3.92
99
5.15
99.73
6
Table 3. Values of Z
0
for Given Confidence
Calculate the % Contribution of each of the components of variation
using the following equation.
% Contribution
=
x 100
Component
Total
2
Determine if the % Contribution (Repeatability) is acceptable using
the following guideline:
If % Contribution (Repeatability) is small (i.e. < 5% or less), then it is
acceptable. This will help ensure attainment of acceptance of %
Contribution (R&R). If the % Contribution (Repeatability) is
greater than 5%, then the measurement system may not be
adequate for this application.
Calculate the % Contribution (R&R) using the following equation:
% Contribution (R&
R)
=
x 100
where
=
R&R
Total
R&R
Repeatability
2
Reproducibility
2
2
Determine if the % Contribution (R&R) is acceptable using the
following guideline:
