Trend Detection - Instability, Cp, Cpk
All trend detection is done by highlighting the plot line where the trend occurs and adding a label at the top of the plot indicating the trend that was found. You can optionally configure settings like which trends should be detected and how many points constitute a particular trend. You can also toggle trend detection on and off.
Instability Tests
The instability tests performed by QC-CALC are:
- Single Point outside the 3 Sigma, Control, or Specification limit
- 2 Sigma Exception
- 1 Sigma Exception
- Center Line Exception
Single Point
3 Sigma Limits – A single point falls outside the 3-sigma limit (beyond zone A).
Control Limits – A single point falls outside the Control Limits.
Spec Limits - A single point falls outside the Specification Limits.
Center Line Represents
You have the option of specifying exactly what the Center Line represents. The two choices are either the Nominal or a Fixed Average. This choice does not affect the appearance of your graphs. It is used solely in the computation of Trend Detection. The Center Line tells QC-CALC where to begin the Sigma Zones.
Cp / Cpk Exception
Calculated Cp and Cpk are compared to the entered Cp and Cpk values. When the actual Cp or Cpk is less then the value of Cp or Cpk entered in the text-box QC-CALC will trigger a Cp or Cpk Exception.