Two-Sided Confidence Limits for Cp
/****************************************************************/
/* S A S S A M P L E L I B R A R Y */
/* */
/* NAME: CPCON */
/* TITLE: Two-Sided Confidence Limits for Cp */
/* PRODUCT: QC */
/* SYSTEM: ALL */
/* KEYS: Capability Analysis, Capability Indices, */
/* PROCS: CAPABILITY */
/* DATA: */
/* */
/* REF: Chou Y., Owen D. B., Borrego S. A. (1990). "Lower */
/* Confidence Limits on Process Capability Indices." */
/* Journal of Quality Technology 22, pp. 223-229. */
/* */
/* NOTES: This program calculates confidence limits for Cp */
/* using the method described on page 224 of COB */
/* (1990). */
/* MISC: */
/* */
/* Examples in the documentation were created using the */
/* statement: ods listing style=statistical; */
/* */
/****************************************************************/
options ps=60 ls=80;
data a;
input x @@;
cards;
1.38 1.49 1.43 1.60 1.59
1.34 1.44 1.64 1.83 1.57
1.45 1.74 1.61 1.39 1.63
1.73 1.61 1.35 1.51 1.47
1.46 1.41 1.56 1.40 1.58
1.43 1.53 1.53 1.58 1.62
1.58 1.46 1.26 1.57 1.41
1.53 1.36 1.63 1.36 1.66
1.49 1.55 1.67 1.41 1.39
1.75 1.37 1.36 1.86 1.49
;
proc capability data=a noprint;
var x;
specs lsl = 0.8 usl = 2.4;
output out = summary
n = n
mean = mean
std = std
lsl = lsl
usl = usl
cp = cp;
data summary;
set summary;
* Assign parameters;
level = 0.95;
lcl = cp*sqrt(cinv((1-level)/2 ,n-1)/(n-1));
ucl = cp*sqrt(cinv(1-((1-level)/2),n-1)/(n-1));
output;
title 'Two-Sided 95% Confidence Limits for Cp';
proc print data = summary noobs;
var lcl cp ucl n mean std lsl usl;
run;
title;