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44 APPENDIX E- PRECISION STATEMENT FOR AASHTO T180
45 X. Precision and Bias Precision Statement for AASHTO Standard Test Method T180, Moisture-Density Relations of Soils Using a 4.54-kg (10-lb) Rammer and a 457-mm (18-in.) Drop X.1 Precision - Criteria for judging the acceptability of maximum dry density and optimum water content results obtained by this method are given in Table X. X.1.1 Single-Operator Precision (Repeatability) â The figures in Columns 2 of Table X are the within standard deviations that have been found to be appropriate for the conditions of tests described 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 values given in Table X, Column 3. X.1.2 Multilaboratory Precision (Reproducibility) â The figures in Column 4 of Table X are the between standard deviations that have been found to be appropriate for the conditions of tests described 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 values given in Table X, Column 5. Table X â Precision Estimates Conditions of Test and Test Property Standard Deviation (1s)a Acceptable Range of Two Test Results (d2s)a Standard Deviation (1s)a Difference Between Two Tests (d2s)a Maximum Dry Density (lb/ ft3): Sandy clay 0.6 1.8 1.6 4.4 Sand and Gravel 0.7 2.1 1.8 5.0 Moisture Content (%): Sandy Clay 0.4 1.0 0.7 2.0 Sand and Gravel 0.3 0.9 0.5 1.4 a These values represent the 1s and d2s limits described in ASTM Practice C670 Single Operator Precision: Multilaboratory Precision: Note â The precision estimates given in Table X are based on the analysis of test results from AMRL interlaboratory study (ILS) and proficiency sample Program (PSP). The ILS data consisted of results from 21 to 23 laboratories tested three replicates of four sets of samples. The materials included coarse and fine- graded aggregate-soil blends with about 7% passing #200. The average maximum density ranged from 138.5 lb/ft3 to 147.7 lb/ft3. The average optimum water contents ranged from 4.5% to 5.9%. The PSP data consisted of results from 144 to 253 laboratories tested pairs of three sets of Soil Classification and Compaction Proficiency samples. The materials included fine grained soil with 85% or more passing #200. The average maximum density ranged from 125.8 lb/ft3 to 132.6 lb/ft3 X.2 Bias â No information can be presented on the bias of the procedure because no comparison with the material having an accepted reference value was conducted. . The average optimum water contents ranged from 8.0% to 10.4%. The details of this analysis are in NCHRP Web-Only Document 168.
