Which term describes errors that shift all measurements in a standardized way, reducing accuracy?

• A. Random error
• B. Systematic error
• C. Instrument error
• D. Human error

Answer: (B)

Systematic error describes errors that shift all measurements by a fixed amount, creating a consistent bias in the results. This happens when something in the instrument or method is off in a reproducible way—like a scale that reads 2 units high every time. Because every measurement is biased in the same direction, the average you obtain is away from the true value, so accuracy drops. The readings may still be tightly clustered if random fluctuations are small, which means precision can be high even though accuracy is low. In contrast, random errors vary unpredictably from one measurement to the next, producing scatter around the true value and primarily affecting precision rather than causing a constant bias. Instrument or human factors can contribute to systematic error, but the defining feature here is the uniform, direction-specific shift in all measurements.