Reliability of intervention implementation. The intervention may be implemented in different ways from occasion to occasion, or, if different practitioners are involved, from practitioner to...

Reliability of intervention implementation. The intervention may be implemented in different ways from occasion to occasion, or, if different practitioners are involved, from practitioner to practitioner. This decreases the chances of obtaining true differences and may make an effective intervention appear ineffective. Example: An agency administrator noticed that an intervention used widely in her agency did not appear effective when the results of the intervention were pooled for all practitioners using the intervention. She suspected that the reason for this was that practitioners were implementing the intervention in a variety of ways. In order to promote standardization, she and the practitioners produced a manual to describe specific steps of the intervention that all could follow.