[bland-altman-basic] bland-altman: Bland-Altman Agreement Plot

[MarkusNeusinger]

Plot Request

Agreement plot between two measurements with limits of agreement.

Use Cases

• Method comparison studies
• Medical device validation
• Measurement reliability

Expected Features

• Difference vs average plot
• Mean difference line
• ±1.96 SD limits of agreement

[claude]

✅ Spec ID: bland-altman-basic

Rationale: The Bland-Altman plot is a well-established method comparison technique in biostatistics and clinical research. This is a unique plot type not covered by existing specs - distinct from scatter plots as it specifically shows difference vs. average with limits of agreement.

Add label approved to begin generation.

[github-actions]

✅ Specification Ready: bland-altman-basic

PR: #2041

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specification.md

bland-altman-basic: Bland-Altman Agreement Plot

Description

A Bland-Altman plot (also known as a difference plot or Tukey mean-difference plot) visualizes the agreement between two measurement methods by plotting the difference against the average of paired observations. It displays the mean difference (bias) as a horizontal line and limits of agreement (mean ± 1.96 SD) to assess whether the methods are interchangeable within acceptable tolerances.

Applications

• Comparing a new blood glucose meter against a laboratory reference standard in medical device validation
• Assessing inter-rater reliability between two observers measuring the same physiological parameter
• Evaluating whether two analytical chemistry methods produce equivalent results for quality control

Data

• method1 (numeric) - Measurements from the first method or observer
• method2 (numeric) - Corresponding measurements from the second method or observer
• Size: 30-200 paired observations recommended for reliable limits of agreement estimation
• Example: Paired blood pressure readings from two different sphygmomanometers on the same subjects

Notes

• The x-axis shows the mean of each pair: (method1 + method2) / 2
• The y-axis shows the difference: method1 - method2
• Include a horizontal line at the mean difference (bias)
• Include dashed horizontal lines at ±1.96 SD (95% limits of agreement)
• Annotate the mean and limits of agreement values on the plot
• Points should have moderate transparency to reveal overlapping observations

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