Measurement Error
Observational Error
The difference between a measured value and the true value. Every measurement carries some degree of error — understanding its sources is key to good science.
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Origin
The mathematical treatment of observational error traces to Carl Friedrich Gauss, who in his 1809 treatise Theoria Motus Corporum Coelestium introduced the method of least squares alongside a probabilistic model of measurement error, showing that if errors follow a normal distribution, least squares yields maximum-likelihood estimates. He extended the framework in 1823, establishing the foundation of modern error analysis.
Updated February 22, 2026