Reliable Change Index

The Reliable Change Index (RCI) is a statistic that tells whether the change in an individual client's score on a measure, from before to after an intervention, is large enough that it is unlikely to be an artifact of the instrument's measurement error. Introduced by Neil Jacobson and Paula Truax in 1991 as one half of their two-part definition of clinically significant change, it converts a pre-post difference into a standardized value and compares it against a critical cutoff, typically 1.96, so that practitioners and researchers can classify each client as reliably improved, unchanged, or reliably deteriorated.