Supported Statistics

Quality Window performs over 50 separate statistical calculations on your data, and displays the results in the Statistics Box of the individual Quality Window screens.

The following table lists many of the most commonly used statistics.

 

Statistic Abbrev. Explanation
Number of Points N The number of non-null values found in the data selected.
Target Deviation T-Dev The separation between the average and the Target
value of the variable.
Standard Deviation – Population S-pop The square root of the average of the squared distances of the observations from the mean.
Current Standard Deviation C-SD The square root of the average of the squared distances of the observations from the mean based on the current Limit Method.
Standard Deviation – Low SD-low The lowest segmented SD over a given range of data values.
Standard Deviation – Moving Range SD-mr ((Moving Range Average * 3.267) – Moving Range Average)/3
Maximum Max The greatest value of the selected data.
This value will highlight if the maximum value exceeds the specification limits for the variable.
Upper Specification Limit USL Average of all data points plus +4 X the selected SD method
Upper Process Capability Limit UPCL Average of all data points plus +3 X the selected SD method
Upper Warning Limit UWL Average of all data points plus +1.5 X the selected SD method
Average AVG The mathematical average of all data points selected.
Current Average C-AVG The mathematical average of all data points selected based on the current Limit Method.
Lower Warning Limit LWL Average of all data points less -1.5 X the selected SD method
Lower Process Capability Limit LPCL Average of all data points less -3 X the selected SD method
Lower Specification Limit LSL Average of all data points less -4 X the selected SD method
Minimum Min The lowest value of the selected data.
This value will highlight if the maximum value exceeds the specification limits for the variable.
Median Med The middle value of the data set, once numerically sorted.
Obs % OSL O % OSL The percentage of points outside of fixed spec limits.
Obs ppm OSL O ppm OSL The number of points outside of fixed spec limits, expressed in parts per million.
Calc % OSL C % OSL The percentage of points outside of +/- 4SD under the normal curve.
Calc ppm OSL C ppm OSL The number of points outside of +/- 4SD under the normal curve, expressed in parts per million.
Variation Cr The capability ratio describes the size of the process variability relative to the size of the specification range.
Targeting Tz This is determined by dividing the standard deviation into the Target Deviation. This produces a number that measures how well the process is centered on target in standard deviations.
Clearance Cpk Capability Clearance describes the clearance between the process distribution curve and the specification limits in terms of standard deviation.
Coefficient Variation %CV SD divided by average – used to normalize SD so it can be compared to other variables.
Moving Range Average MR-AVG Average of range between all data points.
Moving Range UCL MR-UCL +3 X Moving Range Standard Deviation
Moving Range UWL MR-UWL +1.5 X Moving Range Standard Deviation
Moving Range LWL MR-LWL -1.5 X Moving Range Standard Deviation
Rule Violation Rule Alarms based on limits or consecutive data points.
Sum Sum The total of all data points for a variable.
Last Value LV The last non-null value for the currently selected variable.