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43 APPENDIX F- PRECISION STATEMENT FOR AASHTO T265
44 PRECISION STATEMENT FOR AASHTO T265, STANDARD METHOD OF TEST FOR LABORATORY DETERMINATION OF MOISTURE CONTENT OF SOILS 1 Precision and Bias 1.1 Precisionâ Criteria for judging the acceptability of determining percentage of moisture content of soil using T265 are given in Table 1: 1.1.1 Single-Operator Precision (Repeatability) â The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for percent moisture content of the materials in Column 1. 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) â The figures in Column 2 of Table 1 are the standard deviations that have been found to be appropriate for the percent moisture content of the materials in Column 1. 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 multilaboratory limits given in Table 1, Column 3. Table 1 â Precision Estimates for AASHTO T265 Material and Type Index Standard Deviation a (Percent ) Acceptable Range of Two Results a (Percent) Single-Operator precision: Coarse aggregate-soil blend Fine aggregate-soil blend 0.05 0.16 0.1 0.5 Multilaboratory Precision: Coarse aggregate-soil blend Fine aggregate-soil blend 0.12 0.21 0.3 0.6 a These values represent the 1s and d2s limits described in ASTM Practice C670. Note â The precision estimates given in Table 1 are based on the analysis of test results from AMRL interlaboratory study (ILS). The ILS data consisted of results from 26 to 29 laboratories tested three replicates of four different aggregate-soil blends each having about 7% passing #200 sieve. The average moisture contents of the test specimens ranged from 3 % to 6 %. The details of this analysis are in NCHRP Web-Only Document 164. Biasâ No information can be presented on the bias of the procedure because no comparison with the material having an accepted reference value was conducted.
