What is bias?

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Bias is a systematic error that causes measurements to deviate from the true value. It shows up as a consistent offset in one direction, so every reading tends to be too high or too low by roughly the same amount. This happens when the measurement system is miscalibrated or the method introduces a constant error, such as an instrument that isn’t zeroed correctly or a standard that’s off. Because bias is systematic, simply taking more measurements won’t cancel it out; you fix it by recalibrating or correcting the method.

Random errors due to noise vary unpredictably from one measurement to the next and tend to average out with many readings, so they don’t produce a consistent offset. An instrument’s response time affects how quickly it reaches the true value after a change, not a consistent offset across all readings. The difference between two successive readings indicates change or drift between steps, not an inherent fixed offset.