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.

precision The number of digits to which numbers are represented. For example, if p bits are allocated to the mantissa in the representation of floating-point numbers used in a particular computer, then in that computer floating-point numbers have p bits of precision. In general, the precision of floating-point numbers is proportional to their value (i.e. relative) whereas the precision of fixed-point numbers is absolute (independent of the value).

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

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 ]

precision See ERRORS.