Which type of measurement refers to tests that utilize the same method, conditions, and location for verification?

The term you're looking for is associated with repeated tests that are performed under identical conditions to ensure the accuracy and reliability of the radon measurement process. This type of measurement, called a duplicate measurement, involves taking a second reading at the same location and under the same environmental conditions as the initial measurement.

By conducting duplicate measurements, you can compare the two results to check for consistency and identify any potential errors in the initial readings. This process is crucial in radon measurement because it helps validate the findings and ensures that they are not anomalies caused by factors like equipment malfunction or environmental variations.

The other options pertain to different measurement concepts. For example, spiked measurements involve adding a known quantity of radon to a sample to observe how well the measurement method can detect it; calculated measurements refer to estimations based on mathematical modeling rather than direct testing; and estimation measurements involve making informed guesses rather than obtaining precise readings. Each of these serves unique purposes but does not embody the concept of standardized duplicate verification like the correct choice does.