Alarm Tests

On the Alarm Tests tab of each SPC chart configuration dialog box (for those SPC charts that support alarm indicators), you can configure up to 8 rules. These rules are based on Western Electric Zone Rules and SPC standards. The following table provides a breakdown of which tests apply to specific charts.

Chart Name	Alarm Test 1	Alarm Test 2	Alarm Test 3	Alarm Test 4	Alarm Test 5	Alarm Test 6	Alarm Test 7	Alarm Test 8
XBar	P	P	P	P	P	P	P	P
Range	P			P		P	P
Sigma	P			P		P	P
XBar-R	P	*	*	P	*	P	P	*
XBar-S	P	*	*	P	*	P	P	*
Individual	P	P	P	P	P	P	P	P
Moving XBar	P	P	P	P	P	P	P	P
Moving Range	P			P		P	P
C	P			P		P	P
P	P			P		P	P
Np	P			P		P	P
U	P			P		P	P

X - applicable for the chart indicated.

* - only applicable for XBar part of the chart.

Test 1: Sigma rule

An out-of-control signal is given if one point falls beyond Zone A (Zone A begins at 2 sigmas above/below the center line and ends at 3 sigmas above/below the center line).

Test 2: Three-Successive-Points rule

An out-of-control signal is given if a certain number of points out of a total number of successive points fall on the same side of the center line in Zone A or beyond (Zone A begins at 2 sigmas above/below the center line and ends at 3 sigmas above/below the center line). To use this rule, you must provide both the number of out-of-control points and the total number of successive points. For example, by default, the alarm indicator will be triggered if 2 out of every 3 successive points are within Zone A or beyond.

Test 3: Five-Successive-Points rule

An out-of-control signal is given if a certain number of points out of a total number of successive points fall on the same side of the center line in Zone B or beyond (Zone B begins at 1 sigma above/below the center line and ends at 2 sigmas above/below the center line). To use this rule, you must provide both the number of out-of-control points and the total number of successive points. For example, by default, the alarm indicator will be triggered if 4 out of every 5 successive points are within Zone B or beyond.

Test 4: Run rule

An out-of-control signal is given if a certain number of successive points fall above the center line (in any or all Zones) or if a certain number of successive points fall below the center line (in any or all Zones). This alarm is an indication of sustained process shift. To use this rule, you must provide the total number of successive, out-of-control points. For example, by default, the alarm indicator will be triggered if 9 successive points are on the same side of the center line.

Test 5: Hugging rule

An out-of-control signal is given if a certain number of successive points fall in Zone C, either above/below the center line (Zone C begins at the center line and ends at 1 sigma above/below the center line). This alarm is an indication of an inappropriate sigma. To use this rule, you must provide the number of successive points (default is 15).

Test 6: Trend rule

An out-of-control signal is given if there is a certain number of consecutive increasing or decreasing points. This alarm is an indication of a gradual process shift. To use this rule, you must provide the number of consecutive points (default value is 6).

Test 7: Zig-Zag rule

An out-of-control signal is given if a certain number of consecutive points alternate in an up-down sequence. This alarm is an indication of symptomatic over-control. To use this rule, you must provide the number of consecutive points (default value is 14).

Test 8: Wide Groupings rule

An out-of-control signal is given if a certain number of consecutive points falls outside (above and/or below) Zone C (Zone C begins at the center line and ends at 1 sigma above/below the center line). This alarm is an indication of 2 or more process streams having dramatically different variability. To use this rule, you must provide the number of consecutive points (default value is 8).