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Contents | Index
Individual-X Chart & Statistics Windows
The Individual-X Chart Window displays a control chart based on the subgroup
observations (X) and, optionally, a control chart based on the moving ranges
between successive subgroups (MR).
See also:
SPC Concepts : for related When To Use and Interpreting topics
To Create an Individual-X Chart
General Chart Features
The following analysis results are displayed in the Individual-X Chart &
Statistics Windows:
Row. The sequential row number of the subgroup.
Observation. The observation in the subgroup. Each row will contain one subgroup.
Missing data is indicated by a blank field.
Note: If entries are made in the Short Run Options dialog box, the values
listed are the standardized observations.
Range The moving ranges between successive subgroups.
Warning: If a group is out of control it will be marked with an asterisk immediately
after the range value.
Run Tests: If any subgroups violated the selected run tests, the run test number is
listed in this column. You may view and select the run tests that are applied by
selecting Run Tests from the Options menu.
Below the table, is a listing of the options used in the analysis.
Observation Range: Indicates the groups selected for analysis, as specified in the Chart Options
dialog box. If Auto Drop is ON, groups that were out of control were also
excluded from the analysis. A list of dropped groups is provided at the bottom of
the window.
Auto Drop option: This option is ON if the Auto Drop check box in the Analysis Options dialog
box has been selected. The default for this option is the OFF setting.
Auto Fold option: This option is ON if Folded Normal Curve in the Analysis Options dialog box has been selected.
Any negative values will be considered the absolute value of the measurement.
For each control region (if multiple regions specified in the Stepped Control
Limits dialog box), the control chart limits and center line are displayed.
See:
Individual-X Chart Calculations
Moving Range Chart Calculations
Note:
- The value 3 in the Control Limit equations is replaced by the specified value
of the control limit ordinate set in the Analysis Options.
- If standardization using a dispersion estimate is entered in the Short Run
Options, the center line of the X chart will be at zero, and the average line of
the Moving Range chart at one, regardless of the calculated average and average range of the standardized variable.
Sigma : The process sigma of the subgroups selected for analysis.
Center (PCL) : the midpoint of the calculated (or specified) control limits:
Note:
- If Stepped Control Limits are NOT used and Auto Drop is OFF, then the PCL
will equal the Average.
- If Fixed Limits are used with a Non-Normal Curve fit, the PCL will not be
displayed in the Chart or Statistics window, as it cannot be back calculated for an
unknown curve.
The Statistics window also provides a summary of various statistics and
options used in the analysis:
Control Limits based on: the method of calculation for the control limits, as specified in the Stepped
Control Limits dialog box.
Limits were calculated using the … distribution, as specified in the Analysis Options dialog box.
There were p observations out of control: provides a count of out of control groups.
Dropped Groups: If Auto Drop is on, and the control limits were calculated by the software, a
list of groups is provided which were out of control and subsequently dropped
from analysis.
If Short Run Options have been entered, the following is also shown:
A note will indicate the standardization method used (calculated or entered).
A note will indicate how dispersion was specified.
Following this description is a table listing the
Run: The run number.
MEAN: The mean value used for standardizing the run, as entered by the user or
calculated, based on settings in the Analysis Options dialog box
RANGE: The Range value used for standardizing the run, as entered by the user or
calculated, based on settings in the Short Run dialog box.
Label: The label used to identify the run. If you have selected Match runs with common indicator column, then the run will include all runs matching the specified indicator for that
run.
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