Answer :
Final answer:
To reduce a field sample to test size, ASTM C 702 procedures should be used, involving quartering or sample splitters to ensure a representative test sample. Additionally, variance analysis requires statistical methods, and reducing sampling variance can be accomplished by increasing sample size or improving sampling precision.
Explanation:
To reduce the field sample to a testing size, one should follow the procedures described in ASTM C 702. This standard is designed specifically for preparing concrete aggregates or similar materials when a reduction in sample size is necessary for testing. ASTM C 702 lays out methods such as quartering or using a sample splitter to ensure that the final test sample is representative of the entire batch, which is critical for accurate testing results. This standard provides a structured approach to reducing a larger field sample without significantly altering the characteristics of the sample, thus ensuring that test results are reliable and representative of the original sample's properties.
Regarding the study question about determining the overall variance, variance due to the method, and variance due to sampling, it's essential to apply statistical analyses. The overall variance can be calculated using standard formulas in statistics, while identifying the portions of variance due to method and sampling requires a careful experimental design that isolates these factors. Decreasing the variance due to sampling can be achieved by increasing the sample size, using more precise sampling methods, or ensuring the sample is as representative of the population as possible.