Group vs individual approaches to understanding the clinical significance of differences or changes in quality of life.

This article focuses on the traversing of group and individual levels of quality-of-life data. A deductive approach is used to address the extent to which group data can be used to estimate clinical significance at the individual level. An inductive approach is used to evaluate the extent to which individual change data can be brought to the group level to define clinical significance. Both approaches have benefits and drawbacks. This article addresses how clinical significance can be defined for an individual when the threshold for meaningfulness is drawn from group data. It also addresses the condition under which one can use the same threshold difference for group vs individual differences or changes. A sample inductive approach explores the means to identify a clinically significant result or change, with use of insights from cognitive psychology. In most deductive approaches, the identification of a clinically significant difference or change requires identification of a criterion (or at least an interpretable anchor) against which the significance of a change in respondent score is compared.