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Contents | Index
P-Chart & Statistics Windows
See also:
SPC Concepts : for related When To Use and Interpreting topics
To Create an Attribute Chart
General Chart Features
The following analysis results are displayed in the P-Chart and P-Chart
Statistics windows:
Group: the row number from the Data Editor window
Units: the sample size for the group, as specified in the Chart Options dialog box.
Count: the number of units meeting the condition of interest for that group,
sometimes called the “number of defectives.”
Percent
Warning: An asterisk will appear next to the Percent value in the Statistics
window if the value is out of control. The Chart window will display the message “NOT In Control”
If you have chosen a column for X-Axis Labels in the Chart Format Options dialog box, that column heading with its corresponding entries for each group
will also appear in the Statistics window.
A summary of various statistics and options used in the analysis is provided:
Group Range: Indicates the groups selected by the user for analysis. 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.
Number of groups included in the analysis.
Largest and Smallest sample sizes.
Largest and Smallest Counts.
Auto Drop option: as set in the Analysis Options dialog box.
For each control region (if multiple regions specified in the Stepped Control
Limits dialog box):
UCL, LCL : (chart only) the upper and lower control limits, .
Note:
- Fixed Limits, if entered in the Stepped Control Limits dialog box, will be
used in place of calculated limits.
- If the LCL is calculated as a value less than zero, it will not be displayed
on the Chart window, and will be displayed as 0.0 in the Statistics window.
- If the UCL is calculated as a value greater than one, it will be displayed on
the Chart window and the Statistics window as 1.0.
Average : the average percent
Control Limits based on: the method of calculation for the control limits, as specified in the Stepped
Control Limits dialog box.
Center (PCL): the process center line
Note:
- if Stepped Control Limits are NOT used, Auto Drop is OFF, and neither of the
conditions noted in the following two Notes occur, then the PCL will equal the
Average.
- if the PCL is calculated as a value less than zero, it will not be displayed
on the Chart window, and will be displayed as 0.0 in the Statistics window.
- if the PCL is calculated as a value greater than one, it will not be displayed
on the Chart window, and will be displayed as 1.0 in the Statistics window.
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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