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HISTOGRAM Statement 
See CAPIND in the SAS/QC Sample Library 
Standard capability indices such as C_{pk} are generally considered meaningful only if the process output has a normal (or reasonably normal) distribution. In practice, however, many processes have nonnormal distributions. This example, which is a continuation of Example 4.2 and Example 4.3, shows how you can use the HISTOGRAM statement to compute generalized capability indices based on fitted nonnormal distributions.
The following statements produce printed output that is listed in Output 4.4.1 and Output 4.4.2:
proc capability data=plates; specs lsl=0.3 usl=0.8 alpha=0.05; histogram gap / lognormal(indices) noplot; run;
The PROC CAPABILITY statement computes the standard capability indices that are shown in Output 4.4.1.
Output 4.4.1: Standard Capability Indices for Variable GAPExample 4.2 concluded that the fitted lognormal distribution summarized in Output 4.2.2 is a good model, so one might consider computing generalized capability indices based on this distribution. These indices are requested with the INDICES option and are shown in Output 4.4.2. Formulas and recommendations for these indices are given in "Indices Using Fitted Curves".
Output 4.4.2: Fitted Lognormal Distribution Information

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