Example of gage R&R study (nested)main topic interpreting results session command see also
Example of gage R&R study (nested)In this example, three operators each measured five different parts twice, for a total of 30 measurements. Each part is unique to operator; no two operators measured the same part. You decide to conduct a gage R&R study (nested) to determine how much of your observed process variation is due to measurement system variation.
1 Open the worksheet GAGENEST.MTW.
2 Choose Stat > Quality Tools > Gage Study > Gage R&R Study (Nested).
3 In Part or batch numbers, enter Part.
4 In Operators, enter Operator.
5 In Measurement data, enter Response.
6 Click Options. Under Process tolerance, choose Upper spec - Lower spec, and enter 10.
7 Click OK in each dialog box.
Session window output
Gage R&R Study - Nested ANOVA
Gage R&R (Nested) for Response
Source DF SS MS F P Operator 2 0.0142 0.00708 0.00385 0.996 Part (Operator) 12 22.0552 1.83794 1.42549 0.255 Repeatability 15 19.3400 1.28933 Total 29 41.4094
Gage R&R
%Contribution Source VarComp (of VarComp) Total Gage R&R 1.28933 82.46 Repeatability 1.28933 82.46 Reproducibility 0.00000 0.00 Part-To-Part 0.27430 17.54 Total Variation 1.56364 100.00
Process tolerance = 10
Study Var %Study Var %Tolerance Source StdDev (SD) (6 × SD) (%SV) (SV/Toler) Total Gage R&R 1.13549 6.81293 90.81 68.13 Repeatability 1.13549 6.81293 90.81 68.13 Reproducibility 0.00000 0.00000 0.00 0.00 Part-To-Part 0.52374 3.14243 41.88 31.42 Total Variation 1.25045 7.50273 100.00 75.03
Number of Distinct Categories = 1
Gage R&R (Nested) Report for Response |
Graph window output
Gage R&R (Nested) for Response
Look at the %Contribution columns for Total Gage R&R and Part-to-Part. The percent contribution for differences between parts (Part-To-Part = 17.54) is much smaller than the percentage contribution for measurement system variation (Total Gage R&R = 82.46). The %Study Var column indicates that the Total Gage R&R equals 90.81% of the study variation. So, most of the variation is due to measurement system error; very little is due to differences between part. See Guidelines for measurement system acceptability.
A 1 in number of distinct categories tells you that the measurement system is not able to distinguish between parts. See Number of distinct categories statement.
Look at the Components of Variation Graph - located in upper left corner. Most of the variation is due to measurement system error (Gage R&R), while a low percentage of variation is due to differences between parts.
Look at the X Chart - located in the lower left corner. Most of the points in the X chart are inside the control limits when the variation is mostly due to measurement system error.
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