Practice question · Sort into groups
Precision vs. accuracy: classify each archery-style measurement outcome.
Groups: Precise AND accurate · Precise, NOT accurate · Accurate on average, NOT precise
- Readings scattered widely around the true value
- Readings tightly clustered on the true value
- Readings tightly clustered, all 5% too high
- A miscalibrated but very stable instrument
Hints
- Precision = spread (random error). Accuracy = distance from truth (systematic error). They are independent axes.
- A stable instrument gives beautiful, repeatable, and possibly wrong, numbers.
Show the answer
Precise AND accurate: Readings tightly clustered on the true value
Precise, NOT accurate: Readings tightly clustered, all 5% too high, A miscalibrated but very stable instrument
Accurate on average, NOT precise: Readings scattered widely around the true value
Why
Tight grouping and centred grouping are different virtues: repetition improves neither if the sights are bent. Real measurements are judged on both axes at once, and each axis has its own remedy, statistics for precision, calibration for accuracy.
Practise Calibration and Systematic Errors
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