REPRODUCIBILITY STANDARD DEVIATION

REPRODUCIBILITY STANDARD DEVIATION (LET)

Let Subcommand

Compute the reproducibility standard deviation of a variable as defined by the ASTM E 691 - 99 standard.

The reproducibility standard deviation is a core concept defined in the ASTM E 691 - 99 standard. This standard is described in detail in the following document:
"Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method", ASTM International, 100 Barr Harbor Drive, PO BOX C700, West Conshohoceken, PA 19428-2959, USA.

This document describes reproducibility in the following way.

Reproducability is the variability between single test results obtained in different laboratories, each of which has applied the test method to test specimens taken at random from a single quantity of homogeneous material.

The reproducibility standard deviation is computed as

s_R = MAX(s_R,s_r)

with

sR*	=	\( \sqrt{s_{\bar{x}}^2 + s_{r}^2 \frac{n-1}{n}} \)
\( s_{\bar{x}} \)	=	standard deviation of the cell averages
n	=	cell sample size (currently, equal cell sizes expected)

and s_r denoting the repeatability standard deviation

\( s_r = \sqrt{\sum_{i=1}^{p}{s_{i}^2}/p} \)

with p and s_i denoting the number of laboratories and the standard deviation of the i-th laboratory, respectively.

In an interlaboratory study, the reproducibility standard deviation is computed for each material.

LET <par> = REPRODUCIBILITY STANDARD DEVIATION <y> <labid>
                        <SUBSET/EXCEPT/FOR qualification>
where <y> is a response variable;
            <labid> is a lab-id variable;
            <par> is a parameter where the reproducibility sd value is saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

LET RSD = REPRODUCIBILITY STANDARD DEVIATION Y LAB
LET RSD = REPRODUCIBILITY STAND DEVI Y LAB SUBSET MAT = 1

The reproducibility standard deviation can be computed for multiple materials with the command
TABULATE REPRODUCIBILITY STAND DEVI Y LABID MATID

The reproducibility standard deviation can be plotted for multiple materials with the command

REPRODUCIBILITY STANDARD DEVIATION PLOT Y LABID MATID

None

REPRODUCIBILITY SD

E691 INTERLAB	= Perform an E691 interlab analysis.
REPEATABILITY STANDARD DEVIATION	= Compute the repeatability standard deviation.

"Standard Practice for Conducting an Interlaboratory Study to Determine the Precision of a Test Method", ASTM International, 100 Barr Harbor Drive, PO BOX C700, West Conshohoceken, PA 19428-2959, USA.

Interlaboratory Analysis

2005/4

 
SKIP 25
READ GLUCOSE.DAT Y LABID MATID
.
LET MATDIST = DISTINCT MATID
LET NMAT = SIZE MATDIST
XLIMITS 1 NMAT
MAJOR XTIC MARK NUMBER NMAT
MINOR XTIC MARK NUMBER 0
XTIC OFFSET 0.5 0.5
Y1LABEL REPRODUCIBILITY SD
X1LABEL MATERIAL
LINE BLANK
CHARACTER X
.
REPRODUCIBILITY SD PLOT Y LABID MATID