Call number:
ZSP-202-117
In:
Research report / Cold Regions Research and Engineering Laboratory, 117
Description / Table of Contents:
Summary: An experiment was designed to investigate operator-variance in the determination of the plastic limit of cohesive soils, independent of sample preparation and hydration time. A standard sample was prepared by dry-mixing commercial clay, "Grundite", with a pure silt. After the sample was hydrated for 3 weeks, five random samples were taken and five replicates performed on each sample. Analysis of variance (AOV) shows that there is no reason to doubt that the sample is homogeneous at the 0.05 level of significance. Random samples were then distributed to five zones of operators, where a zone is defined as a group of operators with similar backgrounds and engineering interests. Two operators from each group performed five replicates. The AOV model used in the analysis is mixed with the upper level fixed and the two lower levels random. The estimated "within" and "between" operator variances are 0. 45 and 4. 18 respectively. The estimated "between zones" contribution to the total sum of squares is negative. No correlation was found between an operator's internal variance and his deviation from the grand mean. On the basis of this experiment, no reason-exists to doubt that an "untrained" operator can obtain results comparable to those of professional operators. The major factor contributing to the total sample variance is the inconsistency between the individual operators who, although able to duplicate their own determinations, do not call the same end point. To minimize between operator variance, a readily prepared standard sample is suggested with which any operator can calibrate his plastic limit determinations against the expected national average.
Type of Medium:
Series available for loan
Pages:
iv, 8 Seiten
,
Illustrationen
Series Statement:
Research report / Cold Regions Research and Engineering Laboratory 117
URL:
https://hdl.handle.net/11681/5857
Language:
English
Note:
CONTENTS
Preface
Summary
Introduction
Sample preparation
Sample homogeneity
Distribution of samples
Analysis
Conclusions and suggested standardization
References
Location:
AWI Archive
Branch Library:
AWI Library
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