I wanted to put up this post long time ago, anyway I didn’t make my wish realize until today because of laziness.
I almost forget this topic since seldom use it, someone show me a GR&R report and ask me to explain, make me busy for the whole afternoon to flip through my training material to refresh my memory.
Thank you Lim PC….
This is how I interpret the GR&R report below.
(Chart interpretation in anti clockwise)

Components of Variation
The sources of variation that are represented in the graph are:
- Total Gage R&R, which is the variation due to the measuring system including multiple operators using the same gage.
- Repeatability, which is the variability in measurements obtained when the same part is measured multiple times by the same operator.
- Reproducibility, which is the variability in measurements obtained when different operators measure the same part.
- Part-to-Part, which is the variability in measurements across different parts.
In a good measurement system, the largest variation component is Part-to-Part variation. If large amounts of variation attributed to Gage R&R, corrective action is needed.
R Chart By Operator
The R chart consists of the following:
- The plotted points, which represent the difference between the largest and smallest measurements on each part measured by the operator. Because the points are arranged by operator, you can see how consistent each operator is.
- The green center line represent the grand average for the process.
- The red control limits, which represent the amount of variation expected for the subgroup ranges. These limits are calculated using the variation within subgroups.
If any of the points on the graph go above the upper control limit (UCL), then that operator is having problems consistently measuring parts. The UCL value takes into account the number of measurements by an operator on a part and the variability between parts. If the operators are measuring consistently, then these ranges should be small relative to the data and the points should stay in control.
All of the parts data are “in control” indicating that the three operators are measuring consistently.
X Chart By Operator
The X-bar chart consists of the following:
- The plotted points represent the average measurement on each part measured by each operator.
- The green center line represent the overall average for all part measurements by all operators.
- The red control limits (UCL and LCL), which are based on how much variability there is between parts and the number of measurements in each average.
Because the parts chosen for a Gage R&R study should represent the entire range of possible parts, this graph should ideally show lack-of-control. Lack-of-control exists when many points are above the upper control limit and/or below the lower control limit.
For the parts data, there are many points beyond the control limits. This indicates that the measurement system is adequate.
Operator * Part ID Interaction
The graph shows the average measurements taken by each operator on each part in the study, arranged by part. Each line connects the averages for a single operator.
Ideally,
- the lines will follow the same pattern
- the part averages will vary enough that differences between parts are clear
For the parts data, the lines follow each other fairly well. The operators may have a problem consistently measuring part 10.
Measure By Operator
The graph shows all of the measurements taken in the study, arranged by operator. The measurements are represented by dots; the means by the circle-cross symbol. The black line connects the average measurements for each operator.
Ideally,
- the measurements for each operator will vary an equal amount
- the part averages will vary as little as possible
For the parts data, this seems to be the case. There will always be some variation, but it appears the operators are measuring consistently.
Measure By Part ID
The graph shows all of the measurements taken in the study, arranged by part. The measurements are represented by dots; the means by the circle-cross symbol. The black line connects the average measurements for each part.
Ideally,
- the multiple measurements for each individual part will vary as little as possible (the dots for one part will be close together)
- the averages will vary enough that differences between parts are clear
For the parts data, the measurements for part 10 vary quite a bit. This variation may be due to the system’s (operator and/or gage) inability to consistently measure that part. The averages also vary significantly. This variation in averages should occur because the parts chosen for the study should represent the entire range of possible parts.