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PubMed · 7564793

Comparing methods of measurement: why plotting difference against standard method is misleading.

J M Bland·D G Altman
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Abstract

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.

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J M Bland, D G Altman. 1995-10-21. Comparing methods of measurement: why plotting difference against standard method is misleading.. https://doi.org/10.1016/s0140-6736(95)91748-9

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