Page 235 - The Six Sigma Project Planner

and C tended to get different results for the different weeks. Otherwise, the
system appears to be relatively stable.
5. Reproducibility of Inspectors A and B is not perfect. Some benefit might be
obtained from looking at reasons for the difference.
6. Since Inspector B’s results are more accurate and repeatable, studying her might
lead to the discovery of best practices.

MINITAB Attribute Gauge R&R Example
MINITAB includes a built-in capability to analyze attribute measurement systems,
known as “attribute gauge R&R.” We will repeat the above analysis using MINITAB.
MINITAB can’t work with the data as shown in Table 20; it must be rearranged. Once
the data are in a format acceptable to MINITAB, we enter the Attribute Gauge R&R
Study dialog box by choosing Stat > Quality Tools > Attribute Gauge R&R Study. (See
Figure 40.) Note the checkbox, “Categories of the attribute data are ordered.” Check this
box if the data are ordinal and have more than two levels. Ordinal data means, for
example, a 1 is in some sense “bigger” or “better” than a 0. For example, we ask raters
in a taste test a question like the following: “Rate the flavor as 0 (awful), 1 (OK), or 2
(delicious).” Our data are ordinal (“acceptable” is better than “unacceptable”), but there
are only two levels, so we will not check this box.

218