pre·ci·sion / priˈsizhən/ • n. the quality, condition, or fact of being exact and accurate: the deal was planned and executed with military precision. ∎ [as adj.] marked by or adapted for accuracy and exactness: a precision instrument. ∎ technical refinement in a measurement, calculation, or specification, esp. as represented by the number of digits given: this has brought an unprecedented degree of precision to the business of dating rocks | a precision of six decimal figures. Compare with accuracy.
It is important not to confuse the term precision with accuracy. For example, the number 3.142 8571
has eight-decimal digit precision, irrespective of what it represents. If this number represents 22/7 then it is also accurate to eight decimal digits but if it represents the irrational number π then it is accurate only to three decimal digits.
Precision refers to the ability to repeat the same measurement and arrive at the same value. In statistics , precision refers to the difference between repeated measurements of the same quantity, where the closer the measurements are to each other; the greater the precision of the estimate of the quantity. Precise measurements are not necessarily accurate measurements, because the repeated measurements can be very close to the same value and still be far from correct. As an example, if the differences in ten measurements of the same distance are very close to each other, the distancemeasuring device is considered to be precise. However, there is no surety that the distance measured is correct unless the device is also accurate.
[Marie H. Bundy ]