Comparing methods of measurement: why plotting difference against standard method is misleading
Abstract
Summary
When comparing a new method of measurement with a standard method, one of the things we want to know is whether the difference between the measurements by the two methods is related to the magnitude of the measurement. A plot of the difference against the standard measurement is sometimes suggested, but this will always appear to show a relation between difference and magnitude when there is none. A plot of the difference against the average of the standard and new measurements is unlikely to mislead in this way. We show this theoretically and by a practical example.
References (8)
- Dg Altman et al.
Measurement in medicine: the analysis of method comparison studies
Statistician
(1983) - Jm Bland et al.
Statistical methods for assessing agreement between two methods of clinical measurement
Lancet
(1986) - A. Close et al.
Finger systolic pressure: its use in screening for hypertension and monitoring
BMJ
(1986)
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