violence itself, or causative factors related to violence, are in many cases ill-defined or not representative of the intended behavior.

The reactions of other people and the institutional procedures that intervene between an occurrence of violence and a recorded instance of violence are often complex and extended in time, so that records related to violence are often difficult for researchers to interpret in the context of construct validity. For example, a past history of arrests for violent crimes is not synonymous with being a violent person, nor are recorded instances of "aggression," however defined. When histories of arrests for violent crimes are studied without addressing the question of what they represent, or by indirection leaving the implication that the data indicate whether or not the person is violent, construct validity is violated. Similarly, short follow-up periods for collecting data about persons predicted to be violent or not violent may not permit obtaining valid measures of the construct of interest.

Inadequate construct validity also occurs in independent variables used in violence research. For example, a recorded history of psychiatric treatment does not signal or characterize any clearly articulable past pattern of behavior, so its relationship to contemporaneous or future violence, if any, is difficult at best to interpret. Even many variables that superficially appear to have good construct validity because they involve "hard scientific tests" may on closer inspection be inadequate. For example a positive urine test for opiates is not a valid measure of addiction. A more valid but "softer" measure of addiction is a police officer's notation that an arrestee possessed "works," had recent track marks and ulcers, and showed signs of withdrawal irritability.

Criterion Validity Criterion validity deals with the existence of a relationship between test scores, subgroups, or independent variables and actual behavior, as represented by other measurements or observations (Golden et al., 1984). Criterion validity can be measured concurrently or predictively, whether or not the underlying study itself was predictive. Concurrent criterion validity involves showing that there is a relationship with an alternative method of measuring the same characteristic of interest at the same time, whereas predictive validity attempts to show a relationship with the behavior of interest at a future time. Both classification and prediction studies may be examined for their predictive validity.

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