A Panorama QC folder offers several plot types useful in quality control:
Levey-Jennings Plots
The default plot in a Panorama QC folder is the Levey-Jennings plot which is helpful in visualizing and analyzing trends and outliers. The distance between a given observation and the mean (expected value) is measured in standard deviations (SD). For a walkthrough of plotting features featuring these plots, see
Panorama QC Plots.
Moving Range Plots
The moving range can be plotted over time to monitor process variation for individual observations by using the sequential differences between two successive values as a measure of dispersion.
Moving Range (MR) plots can be displayed alongside Levey-Jennings plots for integrated analysis of changes. To create a Moving Range plot, check the box in the QC Plots web part.
In this screencap, both the Levey-Jennings and Moving Range plots are shown side by side. Notice the two elevated points on the moving range plot highlight the one peak (two large changes). Otherwise the value for retention time remained quite consistent.
The plotting features outlined in
Panorama QC Plots also apply to Moving Range plots.
CUSUM Plots
A
Cumulative Sum (CUSUM) plot is a time-weighted control plot that displays the cumulative sums of the deviations of each sample value from the target value. This can highlight a problem when seemingly small changes combine to make a substantial difference over time.
The legend for the dotted and solid lines is included on a CUSUM plot:
- CUSUM- is a solid line
- CUSUM+ is a dotted line
The plotting features outlined in
Panorama QC Plots also apply to both types of CUSUM plots.
CUSUMm (Mean CUSUM)
The CUSUMm (mean CUSUM) plots two types of CUSUM statistics: one for positive mean shifts and one for negative mean shifts.
CUSUMv (Variable CUSUM)
The CUSUMv (variability or scale CUSUM) plots two types of CUSUM statistics: one for positive variability shifts and one for negative variability shifts. Variability is a transformed standardized normal quantity which is sensitive to variability changes.
A sample CUSUMv plot, shown with no other plot type selected:
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