Sources of variation in biomarkers
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Updated: Oct 8, 2026

Identification of Disease-related Spatial Covariance Patterns using Neuroimaging Data
Published on: June 26, 2013
1Dipartimento di Scienze Biomediche e Oncologie Umana, Ospedale di S. Giovanni Battista, Torino, Italy.
Abstract:
Epidemiology is interested in variation. The goal of epidemiological research is to infer cause-effect relationships by observing whether the occurrence of disease varies according to relevant exposures. Epidemiology is usually interested in 'intergroup' variation (e.g. between those who are exposed and those who are unexposed to the factor of interest), while 'intragroup' variation is a source of noise. Therefore, the study design aims to increase intergroup variability, to limit intragroup variability and to reduce error by ensuring validity and reliability of measurements. The goal of this chapter is to summarize simple ways to recognize the main sources of measurement error and to estimate the extent and the impact of such error.
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