Which type of error affects precision?

• A. Random error
• B. Systematic error
• C. Calibration error
• D. Deterioration of reagent

Answer: (A)

Precision is about how closely repeated measurements cluster together. Random error causes unpredictable fluctuations in each measurement, so the results scatter around the true value and the spread increases. That increased scatter is exactly what reduces precision.

Systematic error, in contrast, would shift all measurements by a consistent amount, affecting accuracy (how close the measurements are to the true value) rather than their spread. Calibration error is a type of systematic bias, and deterioration of reagent can introduce bias or variability, but the defining feature that lowers precision is random error—hence it’s the correct focus here.