Not sure why a point on a control chart is marked unstable?

QI Macros "show - hide control chart rule numbers" tells you why.

Example of a typical control chart with out of control points.

control chart

To view which control chart rules have been violated:

  1. Click on the QI Macros chart menu and choose Show/Hide Rule Numbers.
    show hide rule numbers on menu
  2. QI Macros will update the chart with the control chart rule numbers that have been flagged:

    control chart rule violations
  3. In this case, there's one point outside the UCL (1), two points above 2 Sigma (2) and a downward trend (5).
  4. Also, the flagged cell values will turn orange. And when you hover over the cells with a red triangle in the top right corner, you will be provided with a brief description of the violated rule(s):
  5. control-chart-rules-cell-description

Control chart rule numbers and options in QI Macros

QI Macros defaults to Montgomery control chart rules. Use QI Macros menu to easily switch between control chart rules used by various industries.

control chart rules

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