Accuracy is defined as:

• A. How close measured value is to the true value
• B. How long a measurement takes
• C. The precision across trials
• D. The energy resolution of the detector

Answer: (A)

Accuracy is about how close your measured result is to the true value. In XRF analysis, you’re aiming for readings that match the real element concentration or thickness, which you ensure through proper calibration and matrix corrections to minimize instrument bias. The other ideas describe different aspects: the time taken for a measurement relates to workflow and counting statistics but not closeness to the true value; precision refers to how consistent results are across repeated trials, not how close they are to the true value; and energy resolution is about the detector’s ability to distinguish different X-ray energies, not the accuracy of a single measurement. So the correct definition of accuracy is the closeness of the measured value to the true value.