Testing of industrial products - Aggregates for construction

Precision values obtained from the cross-testing experiment on the Sand Equivalent test

Note 1. For all the tables here, "stragglers" have been included in the calculations, and "outliers" have been excluded.

Note 2. See the formulae for the special definition of coefficient of variation used with the Sand Equivalent test.


Table 1. Repeatability and reproducibility values.
Level 1Level 2Level 3
Number of laboratories included N313131
Average X40.155.557.2
Repeatability standard deviation Sr10.921.001.17
Reproducibility standard deviation SR17.593.953.38
Critical range Wc3.22.93.4
Repeatability limit r12.62.83.3
Reproducibility limit R121.211.19.5

Table 2. Functional relations for Sand Equivalent test for SE values (X) in the range 40 <= X <= 60 SE units.
Functional relationship
Repeatability standard deviation Sr1 = 0.5 + 0.0108 (100 - X)
Reproducibility standard deviation SR1 = 0.5 + 0.0884 (100 - X)
Repeatability limit r1 = 1.4 + 0.03 (100 - X)
Reproducibility limit R1 = 1.4 + 0.25 (100 - X)

Table 3. Repeatability and reproducibility standard deviations expressed as coefficients of variation.
Level 1Level 2Level 3
Repeatability coefficient of variation Cr11.52.22.7
Reproducibility coefficient of variation CR112.78.97.9