Look up Shewhart control chart constants

Returns the classical Shewhart constants (A2, A3, c4, d2, d3, B3-B6, D3-D4) for a given subgroup size n. Tabulated values are used for n <= 25; for larger samples, c4 is computed from its closed form and the remaining constants are derived analytically when known (otherwise NA is returned with a warning).

Usage

shewhart_constants(n)

Arguments

n

Integer scalar or vector. Subgroup size (>= 2).

Value

A data frame with columns n, A2, A3, c4, d2, d3, B3, B4, B5, B6, D3, D4.

References

Montgomery, D. C. (2019). Introduction to Statistical Quality Control (8th ed.). Wiley. Appendix VI.

Examples

shewhart_constants(5)
#>   n    A2    A3   c4    d2    d3 B3    B4 B5    B6 D3    D4
#> 1 5 0.577 1.427 0.94 2.326 0.864  0 2.089  0 1.964  0 2.114
shewhart_constants(c(2, 5, 10, 25))
#>    n    A2    A3     c4    d2    d3    B3    B4    B5    B6    D3    D4
#> 1  2 1.880 2.659 0.7979 1.128 0.853 0.000 3.267 0.000 2.606 0.000 3.267
#> 2  5 0.577 1.427 0.9400 2.326 0.864 0.000 2.089 0.000 1.964 0.000 2.114
#> 3 10 0.308 0.975 0.9727 3.078 0.797 0.284 1.716 0.276 1.669 0.223 1.777
#> 4 25 0.153 0.606 0.9896 3.931 0.708 0.565 1.435 0.559 1.420 0.459 1.541