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The homogeneity of samples for bulk specimens as well as glasses or metals and also for powder pellets can be determined by measurements at different specimen positions with a position-sensitive instrument; some examples are shown in Section 16.6. It is also possible to determine inhomogeneities by repeated measurements after the removal of sample layers. In this case, inhomogeneities perpendicular to the surface of the sample can be identified, in other words, layer structures. Furthermore, three-dimensionally distributed inhomogeneities can be detected in this way.

Minor sample inhomogeneities as well as surface roughness can be partially compensated by a rotation of the sample during the measurement.

One possibility for the determination of the reproducibility of the preparation procedure is to repeat several times the entire analysis process including sample preparation, measurement, and evaluation. One can then compare the results obtained from the repeated measurements.

Sufficient homogeneity or reproducibility is achieved if the average value and standard deviation of the results of repeated measurements at the same sample position or on the same sample differ only insignificantly from the results obtained from different sample positions or at different samples. The calculation of the mean value and the standard deviation is shown in Section 6.1.1. Examples for homogeneity tests are discussed in Section 16.6.