Reliable Change Index (RCI) Calculator

How RCI is Calculated

The Reliable Change Index (RCI) helps determine if the change in test scores is statistically meaningful.

Key Formulas

• Standard Error of Measurement (SEM):
  SEM = SD × √(1 - r) = --
  SD = Standard Deviation, r = Reliability coefficient
• Standard Error of the Difference (S_diff):
  Sdiff = √2 × SEM = --
• Reliable Change Index (RCI):
  RCI = (Post - Pre) ÷ Sdiff = --

Interpretation

- An RCI greater than ±1.96 suggests statistically reliable change.
- An RCI between -1.96 and 1.96 indicates the change could be due to measurement error or chance.

References

Jacobson, N. S., & Truax, P. (1991). Clinical significance: A statistical approach to defining meaningful change in psychotherapy research. Journal of Consulting and Clinical Psychology, 59(1), 12–19. https://doi.org/10.1037/0022-006X.59.1.12