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Mathematical coupling does not account for the association between baseline severity and minimally important change
1Department of General Practice, EMGO Institute for Health and Care Research, VU University Medical Center, Van der Boechorststraat 7, Amsterdam, The Netherlands. b.terluin@vumc.nl
Journal of Clinical Epidemiology
|August 2, 2011
Summary
Mathematical coupling affects individual scores but not group-level data. This study shows that baseline severity and minimally important change (MIC) values are genuinely associated, refuting claims that the correlation is spurious due to mathematical coupling.
Area of Science:
- Health Sciences
- Biostatistics
- Clinical Research
Background:
- Studies often report a correlation between baseline severity and minimally important change (MIC) values.
- Browne et al. suggested this correlation may be spurious due to "mathematical coupling."
Purpose of the Study:
- To investigate the impact of mathematical coupling on the correlation between baseline severity and MIC values.
- To determine if mathematical coupling invalidates the observed association between baseline severity and MIC values.
Main Methods:
- The study analyzed the phenomenon of mathematical coupling on individual and group-level scores.
- It demonstrated how shared error variance between baseline and change scores can create spurious correlations at the individual level.
Main Results:
- Mathematical coupling does influence correlations between baseline and change scores at the individual level.
- However, MIC values are determined at the group level, where mathematical coupling does not affect statistics or their correlations.
Conclusions:
- The association between baseline severity and MIC values is not an artifact of mathematical coupling.
- The genuine relationship between baseline severity and MIC values remains valid, irrespective of mathematical coupling concerns.
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