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.
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.
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.
Note
The geometric distribution is quite skewed so it is best to set
conf at the required confidence interval (0 < conf < 1) rather than as
a multiplier of sigma.
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
success <- rbinom(1000, 1, 0.01)
num.noevent <- diff(which(c(1,success)==1))-1
qcc(success, type = "np", sizes = 1)
qcc(num.noevent, type = "g")