Gage R&R Folio: Plots

The following plots are available in gage R&R folios, depending on whether you are using a crossed or nested design. They allow you to visually display the data and examine the precision of the measurement system. For general information on working with plots, see Plots.

The Variation Pie includes several pie charts that allow you to visually examine the sources of variation in the measurements.
- The Total Variation Component chart displays the ratio of each source of variance to the total variance.
- The Gage and Part Variation chart displays the ratio of the total gage variance (reproducibility + repeatability) to the total variance, and the ratio of the part variance to the total variance.
- The Gage R&R Variation chart displays the percentage of repeatability and reproducibility to the total gage variance.
- The Gage Reproducibility chart is available only for crossed designs with the operator * part interaction included in the model. It further decomposes reproducibility to operator variance and operator-part interaction variance.
The Run Chart is available only for crossed designs. Each column shows the measurements that were taken of one part, and the measurements are grouped and color-coded according to the operator who performed the measurements. The blue dotted Mean line is the mean of all the measurements. You can use this plot to look for trends that depend on the operators. For example, this chart could show you that one operator's average measurement is biased to low, or that one part was measured in inconsistent ways.
The Variation Components bar chart shows the contribution of different sources of variation to the total measurement variation. You can use this chart to compare the Part variation to variation that is due to the gage (Repeatability), the operators (Reproducibility) or the sum of both (Total Gage R&R).
The Measurement by Part plot displays the measurements grouped by part. (With nested designs, the x-axis label "Part(Operator)" indicates that one operator measured each part.) The connected red dots in each group are the mean measurements for each part. You can use this plot to study how the variation and mean values depend on the parts. For example, you might conclude from this plot that measurements for one part have less variation than that of the other parts.
The Measurement by Operator plot displays the measurements grouped by operator. The connected red dots in each group are the mean measurements from each operator. You can use this plot to study how the variation and mean values depend on the operator. For example, you might conclude from this plot that one operator tends to record higher values than the others.
The following charts are used to assess the system's reproducibility. The control limits are marked with red dotted lines near the top and bottom of the chart. If one operator is outside the control limits, then that operator's method differs from the others. If all the operators have at least one measurement outside the limits, then the measurement system is overly sensitive to operator technique and has a reproducibility issue.
- The R-Chart by Operator ("R" stands for "Range") is available when 10 or fewer measurements for each part are included. The blue dotted Mean line is the average range of measurements for all operators. Each blue dot represents the range of measurements for a particular part when measured by a particular operator.
- The S-Chart by Operator ("S" stands for "Standard Deviation") is available when more than 10 measurements of each part per operator are included. The horizontal blue line is the average standard deviation of measurements for all operators. Each blue dot represents the standard deviation of measurements for a particular part when measured by a particular operator.
The X-Bar by Operator plot shows how the mean reading changes across the parts. The mean readings are grouped by operator. The blue dotted Mean line is the overall mean of all the measurements. Red dotted lines mark the control limits. Since the control limits are calculated using the repeatability variation, most data points should fall outside the control limits. If they do not, then the system has a repeatability issue.
The Operator * Part Interaction plot is similar to the X-bar by operator plot, except the lines for each operator are color-coded and placed on top of each other. This plot is useful for assessing whether the operator * part interaction has a significant effect on the measurements. If the operator lines are the same shape (i.e., the segments are parallel to each other), the effect is not significant.

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