Which of the following types of control samples may be used to determine precision?

Duplicate samples are essential for determining precision in laboratory analyses. Precision refers to the degree of variability in repeated measurements under unchanged conditions. When duplicates are analyzed, you can compare the results of two samples taken from the same source at the same time. By calculating the difference between these results, you can assess the reproducibility of the method. High similarity indicates high precision, while greater variability implies lower precision.

In contrast, reference samples are typically used to verify the accuracy of a measurement rather than its precision. Blank samples help identify any contamination or background noise in the analysis and are not used for precision determination. Calibration samples serve to establish a relationship between instrument response and concentration but do not provide information on the variability of repeated measurements. Thus, the most effective way to measure precision in analytical testing is through the use of duplicate samples.