Which component of error remains constant or varies in a predictable way over a series of analyses of the same measurand?

• A. Analyst's Error
• B. Uncertainty
• C. Systematic Error
• D. Random Error

Answer: (C)

Systematic error is the bias that shows up in every measurement of the same quantity. It can stay constant, like a fixed offset from miscalibration, or it can vary in a predictable way, such as a proportional bias that scales with the measurand. Because this error is reproducible, it does not cancel out when you average multiple analyses. In contrast, random error arises from unpredictable fluctuations—noise, slight inconsistencies—that do tend to vary freely from analysis to analysis and can average toward the true value as you collect more data. Uncertainty is the overall estimate of how far the true value might be, incorporating both random and systematic contributions, so it’s not a single error component that remains constant. An analyst’s error is a source of bias that falls under systematic error, rather than a separate phenomenon.