Description Usage Arguments Details Value Author(s) Examples
This function builds a u-chart for the Poisson-based count data statistic.
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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). |
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".
Returns a u-chart.
Daniela R. Recchia, Emanuel P. Barbosa
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