Worked example
A scale checks a certified 50.0 g mass. Meter X shows 51.9, 52.0 and 52.1 g. Meter Y shows 49.5, 50.1 and 50.4 g. X varies over 0.2 g but its readings are around 2 g above the reference. Y is less tightly clustered; its mean is 50.0 g in this example.
Contrast and common error
Taking more readings can help characterize random variation. It does not remove a stable calibration error. Averaging the readings of a biased meter can yield a precise mean that remains biased. Use a reference near the operating range before claiming how an offset behaves elsewhere.
Transfer check
A thermometer gives 18.9, 19.0 and 19.1°C for a sample with unknown temperature. Can you claim the meter is accurate? Check: you can describe a 0.2°C range; a reference measurement is needed to assess accuracy.
Try it, then explain it.
Complete a short set without looking at the example. After each answer, explain which evidence or rule supports your decision and why the alternatives do not fit.
Sources & authorship
Original OpenExam explanations and examples. References support the concepts; they are not the source of copied questions. Independent educator review is pending.
OpenStax College Physics 1.3 Accuracy Precision and Significant Figures