HOW TO: Enabling Trend Detection (Instability, Cp, and Cpk)
This explains how to setup the Instability, Cp, and Cpk trend tests.
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written: 06/16/2006
last modified: 05/01/2024


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

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.


  1. Choose Tools > Options.
  2. Expand list on left to the Trend Detection - Instability, Cp, Cpk group.
  3. Choose the trends you would like QC-CALC to detect.
  4. Optionally specify Actions or Report and Log if desired.
  5. Click OK to save changes when finished all changes.
  6. Check the Tools > Trend Detection menu to turn on the Trend Detection functionality in general.

More Information

See related articles on Actions and Report and Log features of trend detection.

Applies To

QC-CALC Real-Time v.3.30
QC-CALC Real-Time v.3.20
QC-CALC Real-Time v.3.00


Trend Detection
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