Environmental Protection Agency (EPA) Lead Risk Assessor Practice Exam

How many samples are recommended for composite wipe sampling to achieve valid results?

1. Less than 4

2. At least 4

3. 5-8

4. More than 10

The correct answer is: At least 4

In the context of lead risk assessment, composite wipe sampling is a method used to measure lead contamination levels on surfaces within a specified area. This technique allows for the collection of samples that represent a broader section rather than focusing on a single location, which can help in assessing the overall contamination levels efficiently. Recommended guidelines suggest that to achieve valid and reliable results from composite wipe sampling, it is advisable to collect at least four samples. This minimum ensures that there is enough data to provide a true representation of lead levels across the surfaces being evaluated. Collecting fewer than four samples may not provide sufficient coverage or statistical power to make meaningful conclusions about contamination levels. Sampling more than this minimum can provide benefits for enhancing accuracy and reliability but is not necessary to meet the basic criteria for valid results. Composite sampling must find a balance between practicality and statistical validity; thus, adhering to the recommendation of at least four samples is key for effective assessment.