Which of the following actions ensures the reliability of sampling results?

Using pre-established methods and protocols is essential for ensuring the reliability of sampling results because these guidelines provide a standardized approach to the sampling process. When specific methods and protocols are followed, it minimizes variability and bias in the sampling process, leading to results that are more trustworthy and reproducible.

Pre-established protocols often include detailed instructions on sampling techniques, equipment, frequency, and handling procedures, which help to reduce human error and ensure consistent results across different sampling events. This level of rigor is crucial in construction materials testing, where accurate soil analysis can significantly impact project outcomes, safety, and compliance with regulations.

In contrast, allowing anyone to sample without oversight could lead to inconsistencies and errors, as untrained personnel may not adhere to the necessary procedures. Randomly taking samples from any location disregards the importance of representative sampling, which can skew results and provide a misleading picture of the material condition. Ignoring variations in stockpile materials would also compromise reliability, as it fails to account for changes in material quality and properties that may affect test results.