REPEATABILITY STANDARD DEVIATION

REPEATABILITY STANDARD DEVIATION (LET)

Let Subcommand

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

The repeatability 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 repeatability in the following way.

Repeatability concerns the variability between independent test results obtained within a single laboratory in the shortest practical period of time by a single operator with a specific set of test apparatus using test specimens taken at random from a single quantity of homogeneous material.

The repeatability standard deviation for a single material is computed as

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

with p and s_i denoting the number of laboratories and the standard deviation of the ith laboratory, respectively.

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

LET <par> = REPEATABILITY 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 repeatability sd value is saved;
and where the <SUBSET/EXCEPT/FOR qualification> is optional.

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

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

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

REPEATABILITY STANDARD DEVIATION PLOT Y LABID MATID

None

REPEATABILITY SD

E691 INTERLAB	= Perform an E691 interlab analysis.
REPRODUCIBILITY STANDARD DEVIATION	= Compute the reproducibility 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 REPEATABILITY SD
X1LABEL MATERIAL
LINE BLANK
CHARACTER X
.
REPEATABILITY SD PLOT Y LABID MATID