A measurement is not perfectly exact. The resolution of an instrument is the smallest change it can display or distinguish. Repeated measurements help reveal the spread of the readings, but repeating does not automatically remove a systematic error.
Example readings: 4.8 g, 5.0 g and 5.2 g.
Mean = (4.8 + 5.0 + 5.2) ÷ 3 = 5.0 g.
Range = highest − lowest = 5.2 − 4.8 = 0.4 g.
One common school estimate uses half the range: 0.4 ÷ 2 = 0.2 g. Report this example as 5.0 ± 0.2 g. This is an estimate based on repeated readings, not a guarantee of the true value. Follow the method stated in the question.
A smaller spread means readings are more precise. Accuracy means closeness to the true value. Readings can be close together but all wrong because of a zero error.
An anomaly is a reading that does not fit the pattern. Investigate or repeat it; do not remove a result just because you dislike it.
| Set | Readings / g | Range / g |
|---|---|---|
| A | 9.8, 10.0, 10.2 | 0.4 |
| B | 9.9, 10.0, 10.1 | 0.2 |
Both means are 10.0 g. Set B has a smaller spread, so it is more precise. This alone does not prove it is more accurate.
Mean = total ÷ number. Range = highest − lowest. Repeats show spread; they do not automatically remove systematic errors.
Build confidence with pictures, clues and instant feedback.
One point for each answer you get right first time.
No timer. Take your time and use a clue whenever you need one.