How do I calculate the reliable change index?

Did a client really change between two assessments, or is the difference within measurement error? Jacobson and Truax (1991). The calculator on this page does it free, without an account, and shows the assumptions behind the answer.

Tool

Reliable change index

Did a client really change between two assessments, or is the difference within measurement error? Jacobson and Truax (1991).

Score before

Score after

Standard deviation of the measure

From a published reference sample (often the test manual or validation paper), not from your client.

Test-retest reliability

From the same source. Use test-retest, not internal consistency, where you can.

For this measure

Functional group mean (optional)

For the clinical significance cut-off c. Leave the four group fields empty to skip it.

Functional group SD (optional)

Clinical group mean (optional)

Clinical group SD (optional)

Nothing you enter is stored or sent anywhere. The calculation runs for this request and is then gone.

Before you use this

Fill in the form and the result appears here, along with every intermediate value and a note on what the number does not mean.

These calculators run on the server with a plain form post, so they work with JavaScript disabled and nothing is sent to a third party.

Reliable change index

Before you use this

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