Phase I X-bar Shewhart Control Chart

Builds the X-bar control chart for Phase I retrospective analysis. The control limits are estimated from the supplied data. Even if the data is not normal, the X-bar statistic is approximately normal by the central limit theorem when subgroup sizes are sufficiently large.

Usage

cchart.Xbar1(x, sizes)

Arguments

x: Phase I data. Matrix or data frame with subgroups in rows.
sizes: Subgroup size(s). A single integer (equal sizes) or a vector.

Value

A list with components x2bar (mean of subgroup means) and sigma (standard deviation), returned invisibly. The control chart is drawn as a side effect.

Phase convention

Phase I --- control limits estimated from the data.

References

Montgomery, D.C., (2009). "Introduction to Statistical Quality Control". Chapter 6. Wiley.

Author

Daniela R. Recchia, Emanuel P. Barbosa

Examples


data(pistonrings)
cchart.Xbar1(pistonrings[1:25, ], 5)