Environmental Protection Agency (EPA) Lead Risk Assessor Practice Exam

What is the recommended number of subsamples to collect per composite for soil sampling?

1. 1-3 subsamples

2. 3-10 subsamples

3. 5-7 subsamples

4. 10-12 subsamples

The correct answer is: 3-10 subsamples

For soil sampling, the recommended number of subsamples to collect per composite is generally established to ensure that the sample is representative and reliable for assessing lead contamination levels. Collecting a range of 3 to 10 subsamples strikes a balance between having enough data points to accurately represent the variability of the site while not overwhelming the evaluator with excessive data that may complicate analysis. This range also allows for the average contaminants in different zones to be captured, providing a clearer picture of the soil quality and any risks associated with lead exposure. The rationale behind this recommendation is rooted in statistical reliability and variance reduction. Collecting fewer than three subsamples may lead to a skewed or unrepresentative composite sample, while gathering too many subsamples, such as over 10, may introduce redundancy and not yield significantly more useful information. Hence, targeting the range of 3 to 10 subsamples is viewed as optimal for maintaining accuracy and efficiency in sampling protocols.