qcc (version 2.2)

oc.curves: Operating Characteristic Function

Description

Draws the operating characteristic curves for a 'qcc' object.

Usage

oc.curves(object, ...)
oc.curves.xbar(object, n, c = seq(0, 5, length=101), 
               nsigmas = object$nsigmas, identify=FALSE, restore.par=TRUE)
oc.curves.p(object, nsigmas = object$nsigmas, identify = FALSE, restore.par=TRUE)
oc.curves.c(object, nsigmas = object$nsigmas, identify = FALSE, restore.par=TRUE)

Arguments

object

an object of class 'qcc'.

identify

logical specifying whether to interactively identify points on the plot (see help for identify).

n

a vector of values specifying the sample sizes for which to draw the OC curves.

c

a vector of values specifying the multipliers for sigma in case of continuous variable.

nsigmas

a numeric value specifying th number of sigmas to use for computing control limits.

restore.par

a logical value indicating whether the previous par settings must be restored. If you need to add points, lines, etc. to a chart set this to FALSE.

...

additional arguments to be passed to the generic function.

Value

• The function invisibly returns a matrix or a vector of beta values, the probability of type II error.

Details

An operating characteristic curve graphically provides information about the probability of not detecting a shift in the process. oc.curves is a generic function which calls the proper function depending on the type of 'qcc' object. Further arguments provided through ...are passed to the specific function depending on the type of chart.

References

Montgomery, D.C. (2000) Introduction to Statistical Quality Control, 4th ed. New York: John Wiley & Sons. Wetherill, G.B. and Brown, D.W. (1991) Statistical Process Control. New York: Chapman & Hall.

See Also

qcc

Examples

data(pistonrings)
attach(pistonrings)
diameter <- qcc.groups(diameter, sample)
beta <- oc.curves.xbar(qcc(diameter, type="xbar", nsigmas=3, plot=FALSE))
print(round(beta, digits=4))
# or to identify points on the plot use
oc.curves.xbar(qcc(diameter, type="xbar", nsigmas=3, plot=FALSE), identify=TRUE)
detach(pistonrings)

data(orangejuice)
attach(orangejuice)
beta <- oc.curves(qcc(D[trial], sizes=size[trial], type="p", plot=FALSE))
print(round(beta, digits=4))
# or to identify points on the plot use
oc.curves(qcc(D[trial], sizes=size[trial], type="p", plot=FALSE), identify=TRUE)
detach(orangejuice)

data(circuit)
attach(circuit)
q <- qcc(x[trial], sizes=size[trial], type="c", plot=FALSE)
beta <- oc.curves(q)
print(round(beta, digits=4))
# or to identify points on the plot use
oc.curves(qcc(x[trial], sizes=size[trial], type="c", plot=FALSE), identify=TRUE)
detach(circuit)