The Specification Limits, Control Limits, Sigma, and Process Capability Distribution properties are associated with control charts and capability.
Specification limits are used when you perform a capability analysis using the Distribution and Capability platforms. Note that in old data tables, the column property might be named Capability Analysis.
You can specify any combination of a Lower Spec Limit, an Upper Spec Limit, or a Target. The Show as Graph Reference Lines option displays the specification limits and target that you specify as reference lines on appropriate plots.
Tip: To add specification limits to several columns at once, see Manage Limits in Quality and Process Methods.
The Control Limits column property enables you to specify control limits for a column, rather that having JMP calculate control limits from the values in the column. This is useful when you are comparing process data to historical control limits.
The Control Limits column property can be assigned only to a numeric column. To assign the Control Limits column property, select the control chart type and then enter the requested values. If any of these entries are missing, JMP replaces it with a calculated value in the control chart.
Use the Sigma property to enter a known sigma value. This value is used by applications such as control charts or any application that requires a sigma value to complete computations. If no sigma value is supplied, sigma is calculated from the sample.
The Process Capability Distribution column property specifies a process distribution for the column. The Process Capability Distribution column property is used only in the Process Capability platform. See also Distribution and Process Capability Distribution.
You can generate automatic alarms by writing a script and storing it as a column property or data table property named QC Alarm Script.
The following QC Alarm Script automatically writes a message to the log whenever a test fails:
Write(
"Out of Control for test ",
qc_test,
" in column ",
qc_col,
" in sample ",
qc_sample
)