Minimal clinically important difference
Short definition
The minimal clinically important difference is the smallest change in an outcome measure that patients or service users perceive as beneficial and that would, on its own, justify a change in care.
In plain language
A difference can be statistically significant and yet so small that no one feels it. This concept helps interpret studies: is the effect found large enough to matter to the person? The value depends on the instrument and the population. On the 0 to 10 numeric pain rating scale, a landmark study in chronic pain (Farrar et al., 2001) linked a reduction of about 2 points, or 30%, to a clinically important improvement.