u-chart

Build normal, Cornish-Fisher corrected, or standardized u charts.

Usage

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

Arguments

x1

Phase I defect counts.

n1

Phase I inspection size or vector of sizes.

type

Chart type: "normal", "cf1", "cf2", or "standardized". Legacy aliases "norm", "CF", and "std" remain supported; "CF" maps to "cf2" because the historical IQCC formula contains both Cornish-Fisher adjustments.

u1

Phase I rates, used instead of x1.

x2

Phase II defect counts.

n2

Phase II inspection size or vector of sizes.

lambda

Known or estimated in-control defect rate.

u2

Phase II rates, used instead of x2.

alpha

Nominal two-sided false-alarm probability.

Value

Invisibly returns the qcc object used to draw the chart.

Details

For Phase I, supply n1 and exactly one of x1 or u1. For Phase II, supply n2 and exactly one of x2 or u2, together with Phase I information or a known lambda.

When inspection sizes vary, the in-control rate is estimated by the pooled Poisson estimator \(sum(x_i)/sum(n_i)\).

Examples

data(moonroof)
cchart.u(x1 = moonroof$yi[1:17], n1 = moonroof$ni[1:17])

cchart.u(x1 = moonroof$yi[1:17], n1 = moonroof$ni[1:17],
         type = "CF", x2 = moonroof$yi[18:34], n2 = moonroof$ni[18:34])

cchart.u(type = "std", u2 = moonroof$ui[18:34],
         n2 = moonroof$ni[18:34], lambda = 1.4)