What dictates the necessity for random sampling in multi-family dwellings?

The necessity for random sampling in multi-family dwellings is driven by the principle that it helps ensure unbiased representation of the entire population of dwellings. When occupants do not know which units will be selected for inspection, it minimizes bias in the sampling process and helps achieve a more accurate assessment of lead exposure risks across the property. This randomness is crucial for maintaining the integrity of the sampling methodology, as it reflects the varied conditions that may exist in different units and does not favor specific areas or demographics within the building.

In contrast, if residents were informed beforehand or if the sampling was dependent on the size of the building or availability of resources, it could introduce systematic biases that compromise the reliability of the assessment. Random selection allows for a broader understanding of lead risks, making it a critical practice in ensuring that the assessment is comprehensive and representative of the overall risk present in the multi-family dwelling.