IQCC (version 0.7)

cchart.u: u-chart

Description

This function builds a u-chart for the Poisson-based count data statistic.

Usage

cchart.u(x1 = NULL, n1 = NULL, type = "norm", u1 = NULL, x2 = NULL,
  n2 = NULL, lambda = NULL, u2 = NULL)

Arguments

x1

The phase I data that will be plotted (if it is a phase I chart).

n1

A value or a vector of values specifying the sample sizes associated with each group for the phase I data.

type

The type of u-chart to be plotted. The options are "norm" (traditional Shewhart u-chart), "CF" (improved u-chart) and "std" (standardized u-chart). If not specified, a Shewhart u-chart will be plotted.

u1

The sample ratios used to estimate the Poisson parameter (lambda). (x1 / n1).

x2

The phase II data that will be plotted in a phase II chart.

n2

A value or a vector of values specifying the sample sizes associated with each group for the phase II data.

lambda

The estimate of lambda.

u2

The sample ratios of the phase II data (x2 / n2).

Value

Returns a u-chart.

Details

For a phase I u-chart, n1 must be specified and either x1 or u1. For a phase II u-chart, n2 must be specified, plus x2 or u2 and either phat, x1 and n1, or u1 and n1. It is important to note that the normal approximation used in the Shewhart u-chart is valid only for n*u large. For small n*p , it should be used an "improved u chart" (with non-normal correction) given by using the argument "CF".

Examples

# NOT RUN {
data(moonroof)
attach(moonroof)
cchart.u(x1 = yi[1:17], n1 = ni[1:17])
cchart.u(x1 = yi[1:17], n1 = ni[1:17], type = "CF", x2 = yi[18:34], n2 = ni[18:34])
cchart.u(type = "std", u2 = ui[18:34], n2 = ni[18:34], lambda = 1.4)

# }