What is the term used to describe material that contains concentrations of the substance being measured and closely resembles the test specimen?

The correct answer is the term "Control," which refers to a material that contains known concentrations of the substance being measured and closely resembles the test specimen. In laboratory testing, controls are essential for ensuring the accuracy and reliability of test results.

Controls are used to verify that the testing procedure is functioning correctly and that the results produced are within acceptable limits. By using a control with known values, a laboratory can confirm that its methods are producing valid results and identify any issues that might arise during testing. This is particularly important in clinical settings, where patient management decisions depend on accurate laboratory data.

Calibration refers to the process of setting or correcting a measuring instrument by adjusting it to match a recognized standard. A blank is a sample that does not contain the substance being measured, used to eliminate background interference in the results. A reference is a standard against which test results can be compared but does not necessarily resemble the test specimen closely. These concepts are distinct from the role of controls in laboratory practice.