qcs.cpn {qcr}

Process capability indices (Nonparametric)

Description

Calculates CNp, CNpm using the formulation described by Tong and Chen (1998).

Usage

qcs.cpn(
  object,
  parameters = c(u = 0, v = 0),
  limits = c(lsl = -3, usl = 3),
  q = c(lq = -3, uq = 3),
  target = NULL,
  median = 0,
  nsigmas = 3,
  confidence = 0.9973
)

Arguments

object

qcs object of type "qcs.xbar" or "qcs.one".

parameters

A vector specifying the u and v parameters values. If parameters = c(u=0, v=0), the cp indice is calculed; If parameters = c(u=1, v=0), the cpk indice is calculed; If parameters = c(u=0, v=1), the cpm indice is calculed; If parameters = c(u=1, v=1), the cpmk indice is calculed.

limits

A vector specifying the lower and upper specification limits.

q

A vector specifying the lower and upper quantiles. These values are necessary, if object value is missing.

target

A value specifying the target of the process. If is NULL, the target is set at the middle value bewteen specification limits.

median

A value specifying the median of data.

nsigmas

A numeric value specifying the number of sigmas to use.

confidence

A numeric value between 0 and 1 specifying the probabilities for computing the quantiles. This values is used only when object values is provided. The default value is 0.9973.

References

Montgomery, D.C. (1991) Introduction to Statistical Quality Control, 2nd ed, New York, John Wiley & Sons.
Tong, L.I. and Chen, J.P. (1998), Lower confidence limits of process capability indices for nonnormal process distributions. International Journal of Quality & Reliability Management, Vol. 15 No. 8/9, pp. 907-19.

Examples

library(qcr)
##' data(pistonrings) 
xbar <- qcs.xbar(pistonrings[1:125,],plot = TRUE)
x<-xbar$statistics[[1]]
LSL=73.99; USL=74.01
median <-median(x)
lq=as.numeric(quantile(x,probs=0.00135))
uq=as.numeric(quantile(x,probs=0.99865))
qcs.cpn(parameters = c(0,0),limits = c(LSL,USL),
       median = median, q=c(lq,uq))
qcs.cpn(object = xbar,parameters = c(0,0), limits = c(LSL,USL))
qcs.cpn(object = xbar,parameters = c(1,0), limits = c(LSL,USL))
qcs.cpn(object = xbar,parameters = c(0,1), limits = c(LSL,USL))
qcs.cpn(object = xbar,parameters = c(1,1), limits = c(LSL,USL))