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Graph description: Comparing methods of measurement: why plotting difference against standard method is misleading, 1

The figure shows a scatter plot of finger systolic blood pressure against arm systolic blood pressure:
finger pressure on the vertical axis, arm pressure on the horizontal axis.
Each point is plotted as a circle and there is a fairly strong positive relationship.
Subjects with high arm pressure tend to have high finger pressure.
The line of equality, on which the points would lie if the two pressures were exactly equal, is also shown.
This is a line at 45 degrees to the two axes. It goes through the middle of the cloud of points.

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

This page maintained by Martin Bland.

Last updated: 12 January, 2004.