Stats.g: Statistics Used In Computing And Drawing A Shewhart G Chart

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qcc (version 2.6)

Description

These functions are used to compute statistics required by the g chart (geometric distribution) for use with the qcc package.

Usage

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

Arguments

data the observed data values center sample center statistic sizes sample sizes (not used) std.dev standard deviation of geometric distribution 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.g() returns a list with components statistics and center.The function sd.g() returns std.dev the standard deviation $sqrt(1-p)/p$.The function limits.g() returns a matrix with lower and upper control limits.

Details

The g chart plots the number of non-events between events. np charts do not work well when the probability of an event is rare (see example below). Instead of plotting the number of events, the g chart plots the number of non-events between events.

References

Kaminsky, FC et. al. (1992) Statistical Control Charts Based on a Geometric Distribution, Journal of Quality Technology, 24, pp 63--69. Yang, Z et. al. (2002) On the Performance of Geometric Charts with Estimated Control Limits, Journal of Quality Technology, 34, pp 448--458.

See Also

qcc

Examples

Run this codesuccess <- rbinom(1000, 1, 0.01) num.noevent <- diff(which(c(1,success)==1))-1qcc(success, type = "np", sizes = 1) qcc(num.noevent, type = "g")

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