Seriously. Not being versed in metrology I took the following fragment from Wikipedia:
A common convention in science and engineering is to express accuracy and/or precision implicitly by means of significant figures. Here, when not explicitly stated, the margin of error is understood to be one-half the value of the last significant place. For instance, a recording of 843.6 m, or 843.0 m, or 800.0 m would imply a margin of 0.05 m (the last significant place is the tenths place), while a recording of 8436 m would imply a margin of error of 0.5 m (the last significant digits are the units).
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Thus, accuracy can be said to be the 'correctness' of a measurement, while precision could be identified as the ability to resolve smaller differences.
The 10:1 test accuracy ratio (TAR) was previously imposed by MIL-STD-45662, but the current thinking per MIL-HDBK-52 is more like 4:1, so 1/4 of the minimum desired resolution is required.
