Consistency is the degree to which logical transitivity is preserved across the individual's judgements. Inconsistency does not necessarily indicate that the decision-maker is wrong: only that he/she has not sorted out his/her mind on the issue concerned.

An individual decision standard indicates whether and how far the individual is acceptably consistent in his/her judgements about priorities. The standard used may be designed in terms of intrinsic norms (variations from 100% absolute consistency), and/or empirical averages (the mean consistency for decision-makers in a profession specialism, company, nation etc). This may be calculated using a consistency algorithm or as eigen value technique (Foster & Algie, 1984, Saaty 1980). The essential logic is straightforward.

A decision-maker may have an obvious ranking inconsistency. He/she may have judgement options A, B and C as follows:


Inconsistency
B warrants more priority than C

C warrants more priority than A.

Logically therefore B should warrant more priority than A

But he/she actually judged that A has more priority than B.








A decision-maker may have a proportionate inconsistency. He/she may have judged options A, B and C as follows:


Proportionate Inconsistency
B warrants four times priority than A.

C is only twice as important as A.

Logically therefore B should warrant more priority than A.

But he/ she actually judged that C has more priority than B.






A decision-maker may have a weighting inconsistency. He/she may have judged options A, B and C as follows:

B warrants twice the priority of C.
C warrants twice the priority of A.
Logically therefore B should have significantly more priority than A.
But the decision-maker actually judged that B warrants only marginally more priority than A.

A decision-maker may have a series of such inconsistencies, some more significant than others. A decision standard pinpoints his/her main inconsistency and assesses the significance of all his/her inconsistencies taken together. Standard validated measures using a trace index with a validated test statistics are incorporated in software programs like Priorities. PDS, BPS, WPS and AHP.

The decision-maker's coherence is given by the extent to which his/her weightings of the options "all things considered" are concordant with his/her composite weights of the options on a criterion-by-criterion basis. A still more rigorous check is whether his/her weightings of the same options expressed in response terms (eg. company supply of relevant products or services to meet market demands).

A team decision standard is an agreement measure that shows whether and how far the team is not only consistent but also concordant (i.e. agrees on priorities), and highlights conflicts between members and/ or their interests.