Description Usage Arguments Details Value Author(s) References See Also Examples

`mandel.k`

calculates Mandel's k statistics for replicate observations.
Mandel's k an indicator of precision compared to the pooled standard deviation across
all groups.

1 2 3 4 5 6 7 8 9 10 | ```
mandel.k(x, g = NULL, m = NULL, na.rm = T, rowname = NULL,
method=c("classical", "robust"), n = NA, ...)
## Default S3 method:
mandel.k(x, g = NULL, m = NULL, na.rm = T, rowname = NULL,
method=c("classical", "robust"), n = NA, ...)
## S3 method for class 'ilab'
mandel.k(x, g = NULL, m = NULL, na.rm = T, rowname = NULL,
method=c("classical", "robust"), n = NA, ...)
``` |

`x` |
An R object (see Details below), which contains replicate observations or,
if |

`g` |
A primary grouping factor, usually corresponding to Laboratory in an
inter-laboratory study. If not present, |

`m` |
A secondary grouping factor, usually corresponding to test item
or measured quantity. |

`na.rm` |
A logical value indicating whether 'NA' values should be
stripped before the computation proceeds. Passed to functions
such as |

`rowname` |
A single character label for the primary grouping factor (e.g. "Lab", "Organisation"). |

`method` |
Character scalar giving the calculation method. |

`n` |
scalar number of observations per group. Required only if |

`...` |
Additional parameters passed to other methods. Currently not implemented. |

`mandel.k`

is a convenience wrapper for mandel.kh(..., type="k"). It is generic,
with methods for numeric vectors, arrays, data frames, matrices and objects of
class `'ilab'`

. All parameters are passed to `mandel.kh`

.

Mandel's *k* is an indicator of relative dispersion for grouped
sets of observations. Given a set of observations *x[i,j,l]* where *i, j, l*
denotes observation *l*, *l=1, 2, ... n* for measurand or test item *j* and group
(usually laboratory) *i*, *i=1, 2, ... p*, Mandel's *k* is given by:

*k=√{\frac{s_{ij}^2}{∑_{i=1}^p{s_{ij}^2/p}}}*

where *s_{ij}* is the standard deviation of values *x_{ijk}* over *k=1, 2, ..., n*.

If `x`

is a vector, one-dimensional array or single-column matrix, values are aggregated
by `g`

and, if present, by `m`

. If `x`

is a data frame or matrix, each column
is aggregated by `g`

and `m`

silently ignored if present. In all cases, if `g`

is `NULL`

or missing, each row (or value, if a vector) in `x`

is taken as a pre-calculated mean (for Mandel's h) or standard deviation (for Mandel's k).

If `x`

is an object of class `'ilab'`

, `g`

defaults to `'$org'`

and
`m`

to `$measurand`

.

The returned object includes a label (`'grouped.by'`

) for the primary grouping factor.
For the `'ilab'`

method, this is "Organisation". For other methods, If `rowname`

is
non-null, `rowname`

is used. If `rowname`

is NULL, the default is `deparse(substitute(g))`

;
if `g`

is also NULL or missing, "Row" is used.

If `method="robust"`

, Mandel's *k* is calculated by replacing the classical pooled standard
deviation with the robust pooled standard deviation calculated by algorithm S (see `algS`

).

mandel.k returns an object of class `"mandel.kh"`

, which is a data frame consisting
of the required Mandel's statistics and in which each row corresponds to a level of `g`

and each column to a level of `m`

or (if `x`

was a matrix or data frame) to the
corresponding column in `x`

. In addition to the class, the object has attributes:

- 'mandel.type'
`"h"`

or`"k"`

- 'grouped.by'
Character scalar giving the label used for the grouping factor

`g`

; see Details above for the defaults.- 'n'
Number of observations per group (

`n`

if specified

S Ellison s.ellison@lgc.co.uk

Accuracy (trueness and precision) of measurement methods and results – Part 2: Basic method for the determination of repeatability and reproducibility of a standard measurement method. ISO, Geneva (1994).

`mandel.h`

, `mandel.kh`

;
`pmandelh`

, `pmandelk`

for probabilities, quantiles etc.;
`plot.mandel.kh`

, `barplot.mandel.kh`

for plotting methods.

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 | ```
data(RMstudy)
#Data frame examples: note no secondary grouping factor
h <- with(RMstudy, mandel.k(RMstudy[2:9], g=Lab))
plot(h, las=2)
#Vector variant
RMstk <- stack(RMstudy[,2:9])
names(RMstk) <- c("x", "meas")
#names replace 'values' and 'ind'
RMstk$Lab <- rep(RMstudy$Lab, 8)
h2 <- with(RMstk, mandel.k(x, g=Lab, m=meas, rowname="Laboratory"))
#Note use of rowname to override g
plot(h2, las=2)
#ilab method
RM.ilab <- with(RMstk, construct.ilab(org=Lab, x=x, measurand=meas,
item=factor(rep("CRM", nrow(RMstk))) ) )
plot(mandel.k(RM.ilab))
#Robust variant
krob <- with(RMstudy, mandel.kh(RMstudy[2:9], g=Lab, type="k", method="robust"))
plot(krob, las=2)
``` |

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