Electron microprobe testing and evaluation procedures to determine
the extent of within- and between-specimen heterogeneity of reference
materials and the experimental uncertainty are described. These
procedures have been developed and used at NIST in the certification of
several NIST Standard Reference Materials (SRMs). In this article, they
have been simplified and updated for general use. Suggestions for
experimental testing of specimens are described and a detailed
description of the statistical evaluation process is included with an
example of a data spreadsheet and instructions for its preparation.
