X-bar Control Chart for Phase I and Phase II

Builds and displays an X-bar control chart for Phase I (retrospective analysis), Phase II (monitoring of future production), or both phases in a single call. When Phase I data is supplied without Phase II data, the chart uses estimated control limits. If Phase II data is supplied without Phase I data, the chart requires x2bars and sigma as reference values.

Usage

cchart.Xbar(
  x1 = NULL,
  n1 = NULL,
  x2 = NULL,
  n2 = NULL,
  x2bars = NULL,
  sigma = NULL
)

Arguments

x1: Phase I data. A matrix or data frame where each row is a subgroup.
n1: Phase I subgroup size(s). A single integer (equal sizes) or a vector.
x2: Phase II data. Same structure as x1.
n2: Phase II subgroup size(s).
x2bars: Mean of subgroup means from Phase I (center line). Can be NULL and computed from x1.
sigma: Standard deviation from Phase I (for control limits). Can be NULL and computed from x1.

Value

Draws the X-bar control chart using qcc. For Phase I only, invisibly returns a list with components x2bar (mean of means) and sigma (standard deviation).

Phase convention

Phase I when only Phase I data is supplied; limits are estimated from the data. Phase II when Phase II data is supplied (with or without Phase I reference 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.Xbar(x1 = pistonrings[1:25, ], n1 = 5)

cchart.Xbar(x1 = pistonrings[1:25, ], n1 = 5, x2 = pistonrings[26:40, ], n2 = 5)

#> List of 11
#>  $ call      : language qcc(data = x2, type = "xbar", center = x2bars, std.dev = sigma)
#>  $ type      : chr "xbar"
#>  $ data.name : chr "x2"
#>  $ data      : num [1:15, 1:5] 74 74 74 74 74 ...
#>   ..- attr(*, "dimnames")=List of 2
#>  $ statistics: Named num [1:15] 74 74 74 74 74 ...
#>   ..- attr(*, "names")= chr [1:15] "26" "27" "28" "29" ...
#>  $ sizes     : Named int [1:15] 5 5 5 5 5 5 5 5 5 5 ...
#>   ..- attr(*, "names")= chr [1:15] "26" "27" "28" "29" ...
#>  $ center    : num 74
#>  $ std.dev   : num 0.00979
#>  $ nsigmas   : num 3
#>  $ limits    : num [1, 1:2] 74 74
#>   ..- attr(*, "dimnames")=List of 2
#>  $ violations:List of 2
#>  - attr(*, "class")= chr "qcc"