A statistical quantity indicating the number of values which could be arbitrarily assigned within the specification of a system of observations. For simple replication
measurements and one estimated parameter (the mean),
More generally, for multivariable computations, the number of degrees of freedom equals the number of observations minus the number of fitted parameters.
PAC, 1994, 66, 595
(Nomenclature for the presentation of results of chemical analysis (IUPAC Recommendations 1994))
on page 599
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic, J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8. doi:10.1351/goldbook