observational error
Bias
(statistics)
Cognitive bias
Correction for measurement error
(for Pearson correlations)
Error
Errors and residuals in statistics
Errors-in-variables models
Instrument error
Measurement uncertainty
Metrology
Outlier
Propagation of uncertainty
Regression dilution
Replication
(statistics)
Statistical theory
Systemic bias
Test method
https://en.wikipedia.org/wiki/Observational_error