Bland Altman Plot

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Bland Altman Plot

The Bland-Altman plot is aimed at comparing two measurement methods [1]. It simply plots the difference between the measurements against their average. The mean difference is the estimated bias, and from the standard deviation of the differences the 95% limits of agreement can be calculated (mean±1.96std).

Bland Altman Plot Configuration

The Bland Altman Plot script shows the following dialog window.

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Two variables have to be defined, which will be sorted so that the correspondence between samples is ensured. The Linear regression convenience option allows getting a scatter plot with a regression line at the same time as the Bland Altman plot.

Bland Altman Plot Results

There are three numeric result tables: the data for the plot (AVR on x-axis, DIFF on y-axis) in the BA table,
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the analysis results in the diff_result table,

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and the equation of the linear regression in the regression table.

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The corresponding plots can be inspected in the plot layout:

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and

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Reference:

1.Bland JM, Altman DG: Statistical methods for assessing agreement between two methods of clinical measurement. Lancet 1986, 1(8476):307-310.