Process Capability Analysis Distribution (Raw Data) - Specifications Tab
Select the Specifications tab of the Process Capability Analysis Distribution (Raw Data) dialog box to access the options described here.
Type
The Type box contains four options: Nominal ± delta; Lower, Nominal, Upper; Lower, Nominal; and Nominal, Upper. Use the Type box to specify which method (see below) you want to use to enter the specification range (see Specifications below). For details regarding these methods and the meaning of the specification range, refer to the Introductory Overview.
Nominal ± delta
When you select Nominal ± delta (the default setting), Statistica expects you to enter the nominal target specification and the deviation (Delta) defining the specification range.
Lower, Nominal, Upper
When you select Lower, Nominal, Upper
Statistica expects you to enter the lower specification limit (LSL), nominal target specification, and the upper specification limit (USL). With this setting, you can thus define a specification range that is asymmetrical about the design center (nominal target).
Nominal value
Select this check box in order to specify a nominal value; clear the check box to omit the nominal value.
Nominal value, ± Delta value, Lower specification limit, and Upper specification limit (Specifications)
Use these options to enter the nominal target specification, Delta value, and the lower and upper specification limits (specification range). The options that are available is dependent upon the setting of the Type box (see above).
User-defined parameter 1
Select the User-defined parameter 1 check box to enter a value for the respective parameter (or adjust the value with the microscrolls).
Sigma limits
These limits will determine the process range that is shown in the summary histogram (Summary histogram button), and that is used for the computation of the normal distribution process (machine) capability indices (Summary: Current variable button). In short, this value will determine what is considered the practical range of values produced by the process. The default setting, 6 times Sigma (± 3 times Sigma), is the commonly recommended value.