Distribution-based measures suggested to determine minimal clinically important difference (MCID)
| Measure | Definition | Suggested MCID |
| Effect size | Standardised measure of change obtained by dividing the difference in scores from baseline to post-treatment by the standard deviation of baseline scores | <0.20: no change 0.20–0.49: small change 0.50–0.79: moderate change ≥0.80: large change |
| Standard error of measurements | It represents the variation in patient-reported outcome scores attributed to instrument unreliability, in which a change smaller than the calculated sem is likely due to measurement error rather than a true change | Threshold values of 1 sem, 1.96 sem and 2.77 sem have been suggested |
| Standard deviation | Measure used to quantify the amount of variation or dispersion of a set of data values | ≥0.5 sd |
| Coefficient of variation | Standardised measure of dispersion of a frequency distribution | ≥1.65 CV |
| Minimal detectable change | The smallest threshold of change in scores that can be considered above the measurement error with a given level of confidence (usually 95% confidence) | ≥MDC |
| Reliable change index | Statistic that determines the magnitude of change score necessary of a given self-report measure to be considered statistically reliable It is calculated by dividing the individual patient change in score by the square root of the sem | ≥1.96 |