Process Capability Analysis Distribution (Raw Data)

1. Select one of the following via the

   Process Capability Analysis Setup--Raw Data

   dialog box

   - Distribution

   tab as the fitting distribution:  
   • Beta
   • Exponential
   • Extreme value (Type I
   • Gumbel), Gamma
   • Log-Normal
   • Normal and general non-normal (Pearson and Johnson fitting) -- Percentile fit
   • Rayleigh
   • Weibull
2. Click the OK button to display the Process Capability Analysis - Distribution (Raw Data) dialog box, which contains four tabs:

   • Quick

   • Specifications

   • Advanced

   • Options

For further information on raw data, see

Process Analysis Procedures

Startup Panel -

Quick

tab.

Summary box

The Summary box at the top of the dialog box displays a summary of the parameters established so far in the analysis.

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. Note that 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. 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.

Variable << >>

If more than one variable is selected for the analyses, you can switch between them via the Variable << and >> buttons (or use the adjacent menu). The specifications for each variable are unique (for example, any user-specified mean, Sigma, or specifications only apply to the current variable, and different variables can have different specifications. (See Specifications for a further description of the terms user-specified mean, Sigma, or specifications).

Summary

Click the Summary button to produce two spreadsheets containing the standard process capability indices and process performance indices. Available process capability indices include Cp, Cr, Cpk, Cpl, Cpu, K, and Cpm. Available process performance indices include Pp, Pr, Ppk, Ppl, and Ppu. These indices are reviewed in Process Capability Indices and Process Performance vs. Process CapabilityIntroductory Overview.

Multiple samples (Cp, Cpk, Pp, Ppk, etc.)

If the input data consist of multiple samples, and you specified a grouping variable with sample identifiers, Statistica estimates the within-sample Sigma based on ranges, standard deviations, or variances, depending on the your selection on the

Process Capability Analysis Setup--Raw Data dialog box - Grouping

tab. This estimate of Sigma is used to compute the capability indices when you select the Summary button on this dialog. The standard deviation for all cases (total variation) is used to compute the performance indices, which will be displayed in a second spreadsheet; the standard deviation for all observations is also used in all other options available on this dialog. Refer to the Introductory Overview for additional details (see also the ASQC/AIAG reference manual; ASQC/AIAG, 1991, page 80). 

Cancel

Click the Cancel button to close the dialog box without performing an analysis and return to the Process Capability Analysis Setup--Raw Data dialog box.

Options

Click the Options button to display the Options menu.