Matrix of runs by factor levels in which each level is denoted by a code that represents the relative magnitude of the level.
Examples: - A two-level design is coded \(-1\) and \(+1\), a three-level design is coded \(-1\), \(0\) and \(+1\).
- In a rotatable central composite design for three factors the coded levels are \(-\sqrt 2\), \(-1\), \(0\), \(+1\), \(+\sqrt 2\).
Source:
PAC, 2016, 88, 407. 'Vocabulary of concepts and terms in chemometrics (IUPAC Recommendations 2016)' on page 414 (https://doi.org/10.1515/pac-2015-0605)