Measuring the reliability of observational data: a reactive process.

Reliability of observational data was measured simultaneously by two assessors under two experimental conditions. During overt assessment, observers were told that reliability would be measured by one of the two assessors, thus permitting computation of reliability with an identified and an unidentified assessor. During covert assessment, observers were not informed of the reliability measured. Throughout the study, each of the assessors employed a unique version of a standard observational code. In the overt assessment condition, reliability of observers with the identified assessor was consistently higher than reliability with the unidentified assessor, indicating that observers modified their observational criteria to approximate those of the identified assessor. In the covert assessment condition, reliability with the two assessors was substantially lower than during overt assessment. Further, observers consistently recorded lower frequencies of disruptive behavior than the two assessors during covert assessment.