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-rw-r--r--man/lod.Rd55
1 files changed, 26 insertions, 29 deletions
diff --git a/man/lod.Rd b/man/lod.Rd
index e6ce345..15f9603 100644
--- a/man/lod.Rd
+++ b/man/lod.Rd
@@ -3,14 +3,9 @@
\alias{lod.lm}
\alias{lod.rlm}
\alias{lod.default}
-\alias{loq}
-\alias{loq.lm}
-\alias{loq.rlm}
-\alias{loq.default}
-\title{Estimate a limit of detection (LOD) or quantification (LOQ)}
+\title{Estimate a limit of detection (LOD)}
\usage{
- lod(object, \dots, alpha = 0.05, k = 1, n = 1, w = "auto")
- loq(object, \dots, alpha = 0.05, k = 3, n = 1, w = "auto")
+ lod(object, \dots, alpha = 0.05, beta = 0.05)
}
\arguments{
\item{object}{
@@ -19,40 +14,42 @@
with model formula \code{y ~ x} or \code{y ~ x - 1},
optionally from a weighted regression.
}
- \item{alpha}{
- The error tolerance for the prediction of x values in the calculation.
- }
\item{\dots}{
Placeholder for further arguments that might be needed by
future implementations.
}
- \item{k}{
- The inverse of the maximum relative error tolerated at the
- desired LOD/LOQ.
- }
- \item{n}{
- The number of replicate measurements for which the LOD/LOQ should be
- specified.
+ \item{alpha}{
+ The error tolerance for the decision limit (critical value).
}
- \item{w}{
- The weight that should be attributed to the LOD/LOQ. Defaults
- to one for unweighted regression, and to the mean of the weights
- for weighted regression. See \code{\link{massart97ex3}} for
- an example how to take advantage of knowledge about the variance function.
+ \item{beta}{
+ The error tolerance beta for the detection limit.
}
}
\value{
- The estimated limit of detection for a model used for calibration.
-}
+ A list containig the corresponding x and y values of the estimated limit of
+ detection of a model used for calibration. }
\description{
- A useful operationalisation of a lower limit L of a measurement method is
- simply the solution of the equation
- \deqn{L = k c(L)}{L = k * c(L)}
- where c(L) is half of the lenght of the confidence interval at the limit L.
+ The decision limit (German: Nachweisgrenze) is defined as the signal or
+ analyte concentration that is significantly different from the blank signal
+ with a first order error alpha (one-sided significance test).
+ The detection limit, or more precise, the minimum detectable value
+ (German: Erfassungsgrenze), is then defined as the signal or analyte
+ concentration where the probability that the signal is not detected although
+ the analyte is present (type II or false negative error), is beta (also a
+ one-sided significance test).
+}
+\references{
+ J. Inczedy, T. Lengyel, and A.M. Ure (2002) International Union of Pure and
+ Applied Chemistry Compendium of Analytical Nomenclature: Definitive Rules.
+ Web edition.
}
\examples{
data(din32645)
m <- lm(y ~ x, data = din32645)
- lod(m)
+ # The decision limit (critical value) is obtained by using beta = 0.5:
+ lod(m, alpha = 0.01, beta = 0.5) # approx. Nachweisgrenze in Dintest 2002
+ lod(m, alpha = 0.01, beta = 0.01)
+ # In the latter case (Erfassungsgrenze), we get a slight deviation from
+ # Dintest 2002 test data.
}
\keyword{manip}

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