Precision Estimates of AASHTO T267: Determination of Organic Content in Soils by Loss on Ignition (2010)

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41 APPENDIX E- PRECISION STATEMENT FOR AASHTO T267

42 PRECISION STATEMENT FOR AASHTO T267, “DETERMINATION OF ORGANIC CONTENT IN SOILS BY LOSS ON IGNITION” 1 Precision and Bias 1.1 Precision - Criteria for judging the acceptability of percent organic content in soils obtained by this method are given as follows: 1.1.1 Single-Operator Precision (Repeatability) – The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for the organic mass percentage of soil samples. Two results obtained in the same laboratory, by the same operator using the same equipment, in the shortest practical period of time, should not be considered suspect unless the difference in the two results exceeds the single-operator limits given in Table 1, Column 3. 1.1.2 Multilaboratory Precision (Reproducibility) – The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for the organic mass percentage of soil samples. Two results submitted by two different operators testing the same material in different laboratories shall not be considered suspect unless the difference in the two results exceeds the multi-laboratory limits given in Table 1, Column 3. Table 1 – Precision Estimates for AASHTO T267 Condition of Test and Test  Property  Standard deviation, %  (1s)  Acceptable Range of Two Results, %   (d2s)  Single-Operator Precision: Clay 0.25 0.72 Silt and Sand 0.19 0.54 Multilaboratory Precision: Clay 0.57 1.60 Silt and Sand 0.35 1.00 a These values represent the 1s and d2s limits described in ASTM Practice C670. Note – The precision estimates are based on the analysis of test results from 27 laboratories participated in an AMRL interlaboratory study. The data consisted of organic content measurements of clay, silt, and sand blends with 2%, 5%, and 8% of organic material. The details of this analysis are in NCHRP Web-Only Document 163. 1.2 Bias– No information can be presented on the bias of the procedure because no comparison with the material having an accepted reference value was conducted.