What is the purpose of minimal important differences (MID)?
Minimal important differences (MID) are the threshold for appreciable benefits and harms, separated by a zone either side of the line of no effect where there is assumed to be no clinically important effect. The MID lines are used to determine if imprecision is serious or very serious based on the 95% CIs for the pooled estimate of effect. If either end of the 95% CI of the overall estimate of effect crosses one of the MID lines, imprecision is regarded as serious. If both MID lines are crossed by either or both ends of the 95% CI then imprecision is regarded as very serious. Anchor-based methods are used to establish clinically meaningful changes in a continuous outcome variable by relating or anchoring them to patient-centred measures of clinical effectiveness that could be regarded as gold standards with a high level of face validity.