Creating a Cumulative Distribution Plot

CDFPLOT Statement

Creating a Cumulative Distribution Plot

See CAPCDF1 in the SAS/QC Sample Library

This section introduces the CDFPLOT statement with a simple example. A company that produces fiber optic cord is interested in the breaking strength of the cord. The following statements create a data set named CORD, which contains 50 breaking strengths measured in pounds per square inch (psi), and they display the cdf plot in Figure 2.1. The plot shows a symmetric distribution with observations concentrated 6.9 and 7.1. The plot also shows that only a small percentage (<5%) of the observations are below the lower specification limit of 6.8.

   data cord;
      label strength = 'Breaking Strength (psi)';
      input strength @@;
   datalines;
   6.94 6.97 7.11 6.95 7.12 6.70 7.13 7.34 6.90 6.83
   7.06 6.89 7.28 6.93 7.05 7.00 7.04 7.21 7.08 7.01
   7.05 7.11 7.03 6.98 7.04 7.08 6.87 6.81 7.11 6.74
   6.95 7.05 6.98 6.94 7.06 7.12 7.19 7.12 7.01 6.84
   6.91 6.89 7.23 6.98 6.93 6.83 6.99 7.00 6.97 7.01
   ;

   title 'Cumulative Distribution Function of Breaking Strength';
   legend1 frame cframe=ligr cborder=black position=center;
   proc capability data=cord noprint;
      spec lsl=6.8 llsl=2 clsl=black;
      cdf strength  / cframe = ligr
                      legend = legend1;
   run;

Figure 2.1: Cumulative Distribution Function

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