qcc (version 1.2)

stats.R: Functions to plot Shewhart R chart

Description

These functions are used to compute statistics required by the R chart.

Usage

stats.R(data, sizes)
sd.R(data, sizes, std.dev, equal.sd = TRUE)
limits.R(center, std.dev, sizes, conf)

Arguments

data

the observed data values

center

sample/group center statistic.

sizes

samples sizes. Optional

std.dev

within group standard deviation. Optional for sd.R function, required for limits.R

equal.sd

a logical indicating whether the standard deviation is constant for all samples/groups.

conf

a numeric value used to compute control limits, specifying the number of standard deviations (if conf > 1) or the confidence level (if 0 < conf < 1).

Value

• The function stats.R returns a list with components statistics and center.

  The function sd.R returns std.dev the standard deviation of the statistic charted.

  The function limits.R returns a matrix with lower and upper control limits.

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