Experimental functional analyses for challenging behavior: a study of validity and reliability.

The convergent validity of an experimental (analog) functional analysis was investigated by a comparison of three separate ways of interpreting the data derived from such an assessment: two previously published methods and the criterion Z method derived by the authors. Data from the experimental functional analysis of the challenging behavior(s) of 27 individuals with intellectual disabilities were analyzed to assess agreement between the three forms of interpretation. The test-retest reliability of all three methods over periods of 2 weeks, 1 month, and 3 months was also calculated. The results suggest that the methods of interpreting function from experimental assessments can give different results and that the test-retest reliability of the experimental functional analyses is poor. The implications of these findings are discussed in relation to clinical practice.