stats.np {qcc}

Statistics used in computing and drawing a Shewhart np chart

Description

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

Usage

stats.np(data, sizes)
sd.np(data, sizes, ...)
limits.np(center, std.dev, sizes, conf)

Arguments

data

the observed data values

center

sample/group center statistic.

sizes

samples sizes.

std.dev

within group standard deviation.

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).

...

further arguments are ignored.

Value

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

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

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

Author(s)

Luca Scrucca

References

Montgomery, D.C. (2005) Introduction to Statistical Quality Control, 5th ed. New York: John Wiley & Sons.
Wetherill, G.B. and Brown, D.W. (1991) Statistical Process Control. New York: Chapman & Hall.

See Also

qcc