Process Capability Analysis Normal and General Non-Normal Distribution (Aggregated Data)
Click the OK button in the Process Capability Analysis Setup Aggregated Data dialog box to display the Process Capability Analysis Normal and General Non-Normal Distribution (Aggregated Data) dialog box, which contains one tab: Quick.
Summary box
The Summary box at the top of the dialog box lists the variables with sample means, sample ranges, and sample sizes. It also displays summary statistics for the data including the number of samples, the overall mean, the average sample size, and the Sigma (computed from the ranges).
Copy button
Click the Copy button to copy either the selected text (if text has been selected) in the Summary box or all of the text (if no text has been selected) to the Clipboard.
The copied text retains formatting information (such as font, color, etc.).
Contract/Expand button
Click the Contract/Expand button to contract or expand the Summary box.
When contracted, you can see only one line of the Summary box text and can scroll through the text using a scroll bar. Note that when contracted the text is scrolled so that the first non-blank line is at the top. When expanded (the default setting), the entire Summary box will be displayed on the Multiple Correspondence Analysis Results dialog.
The Quick tab of the Process Capability Analysis Normal and General Non-Normal Distribution (Aggregated Data) dialog box contains options to specify the engineering tolerances and the Sigma limits to be used for the computation of the capability and performance indices.
Summary: Descriptive statistics
Click the Summary: Descriptive statistics button to display a spreadsheet that contains the engineering tolerances and capability indices (for detailed description of these values see Process Capability Indices).
Type
The Type box contains four options:
Use these options to specify which method (see descriptions below) you want to use to enter the specification range (via Specifications, see below).
For details regarding these methods and the meaning of the specification range, refer to the Introductory Overview.
Nominal ± delta
When the default setting, Nominal ± delta, is selected, 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). In this setting, you can 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 mean
By default, the mean is estimated from the data. However, if the User-defined mean check box is selected, you can specify a different mean value in the adjacent box, or adjust the value using the microscrolls.
User-defined sigma
By default, the process standard deviation (Sigma) is estimated from the data.
However, if the User-defined sigma check box is selected, you can specify a different Sigma value in the adjacent box, or adjust the value using the microscrolls.
Computation of Sigma
- When the Ranges option button is selected on the Process Capability Analysis Setup Aggregated Data - Advanced tab, the within-sample Sigma is estimated as R-bar/d2 (see, for example, Montgomery, 1985, 1991. See also Quality Control).
- When the Standard Deviations option button is selected, Statistica computes the within-sample Sigma as S-bar/c4 (see, for example, Montgomery, 1985, 1991).
- When the Variances option button is selected, Statistica will compute the square root of the average within-sample variance.
Sigma limits
These limits will determine the process range that is used for the computation of the process (machine) capability indices (see Process Capability Indices).
In short, this value determines 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. Note that the limits specified here will be applied to the average within-sample Sigma, computed from the within-sample ranges, standard deviations, or variances.
Summary
Click the Summary button to produce a spreadsheet that contains the engineering tolerances and capability indices (for detailed description of these values see Process Capability Indices).
Cancel
Click the Cancel button to close the dialog box without performing an analysis and return to the Process Capability Analysis Setup Aggregated Data dialog box.