Dataplot Vol 2 Vol 1

# REPEATABILITY STANDARD DEVIATION

Name:
REPEATABILITY STANDARD DEVIATION (LET)
Type:
Let Subcommand
Purpose:
Compute the repeatability standard deviation of a variable as defined by the ASTM E 691 - 99 standard.
Description:
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 si 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.

Syntax:
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.
Examples:
LET RSD = REPEATABILITY STANDARD DEVIATION Y LAB
LET RSD = REPEATABILITY STAND DEVI Y LAB SUBSET MAT = 1
Note:
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
Default:
None
Synonyms:
REPEATABILITY SD
Related Commands:
 E691 INTERLAB = Perform an E691 interlab analysis. REPRODUCIBILITY STANDARD DEVIATION = Compute the reproducibility standard deviation.
Reference:
"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.
Applications:
Interlaboratory Analysis
Implementation Date:
2005/4
Program:

SKIP 25
.
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

NIST is an agency of the U.S. Commerce Department.

Date created: 4/20/2005
Last updated: 10/07/2016