View and Analyze Created Control Charts
Explanation
This activity is used to view and analyze any created control charts.
Open the control chart that you want to view on the p Chart,
np Chart, c Chart, u Chart Xbar and R Chart, Xbar and S Chart
or X and MR Chart page. These pages can also be accessed
from the Control Charts page.
- p Chart - Gives information about the proportion of
nonconforming units.
- np Chart - Gives information about the number of nonconforming
units.
- c Chart - Gives information about the number of nonconformities.
- u Chart - Gives information about the number of nonconformities
per unit.
- Xbar and R Chart - Gives information about the average
and the range of the result set of each analysis selected in the graph.
- Xbar and S Chart - Gives information about the average
and the standard deviation of the result set of each analysis selected in
the graph.
- X and MR Chart - Gives information about individual
results and moving ranges for each analysis selected in the graph.
Control charts are used to analyze a process or its outputs and take appropriate
actions to achieve and maintain a state of statistical control. A process is
in statistical control ("in control") when all special causes of variation
have been eliminated and only common causes remain, i.e., observed variation
can be attributed to a constant system of chance causes.
Several statistical tests (alarm rules) can be used to determine whether
a control chart is "in control" or "out of control":
- Out of Specification: An alarm rule violation will
be triggered when a point in the control chart is above Inner Max or Outer
Max or below Inner Min or Outer Min.
- Above Upper Control Limit: An alarm rule violation
will be triggered when a point in the control chart is above the Upper Control
Limit (UCL).
- Below Lower Control Limit: An alarm rule violation
will be triggered when a point in the control chart is below the Lower Control
Limit (LCL).
- 2 out of 3 beyong 2 sigma: An alarm rule violation
will be triggered when at least two out of three successive points in the
control chart on the same side of the centerline (CL) are beyond the 2 sigma
limit.
- 4 out of 5 beyond 1 sigma: An alarm rule violatin will
be triggered when at least four out of five successive points in the control
chart on the same side of the centerline (CL) are beyond the 1 sigma limit.
- 15 at or within 1 sigma: An alrm rule violation will
be triggered when 15 successive point in the control chart are at or within
1 sigma.
- 8 outside 2 sigma: An alarm rule violation will be
triggered when eight successive points in the control chart are outside
+2 or -2 sigma.
- 8 below or above the centerline: An alarm rule violation
will be triggered when eight successive points in the ocntrol chart are
below or above the centerline.
- Runs up/ down of length 8 or greater: An alarm rule
violation will be triggered when eight successive points in the control
chart are in ascending or descending order.
One or more of these alarm rules may have been activated for the control
plan line (data point). If an alarm rule violation occurs for an activated alarm
rule, information about the alarm rule violation will be displayed in the control
chart.
If you want to see all the measurement data used for the calculations of
the control chart, click Sample Data. If you want to view the analysis
numbers that were excluded when the control charts were created, click Not
Included Sample Data. The graph can be printed by clicking Print
Graph. To view the control chart setup used to create the chart, click
View Setup.
Prerequisites
At least one control chart of the type you want to view must exist.
System Effects
As a result of this activity, any created control chart can be viewed and
analyzed.