K

Kaldor-Hicks Criterion
A criterion of equity which states that one social state is better than another if there is a net gain in efficiency and if those that gain can compensate the losers.

Kendall's tau
A measure of association used to correlate two ordinal scales.

Kenneth Arrow's Impossibility Theorem
A theorem to demonstrate that it is impossible to aggregate individual preferences through majority voting without violating one or more of five reasonable conditions of democratic decision-making.

Known-group Validation
A procedure for validating an instrument which involves testing on a group for which the results are already known. FOR EXAMPLE, testing a self-report instruments on a group of known offenders.

Kurtosis
A term used to describe a curve indicating that it is more peaked than the normal curve.