Biases

Confounding by indication

A distortion that modifies an association between an exposure and an outcome, caused by the presence of an indication for the exposure that is the true cause of the outcome.

Data-dredging bias

A distortion that arises from presenting the results of unplanned statistical tests as if they were a fully prespecified course of analyses.

Detection bias

Systematic differences between groups in how outcomes are determined.

Diagnostic access bias

Individuals differ in their geographic, temporal and economic access to diagnostic procedures which label them as having a given disease.

Diagnostic suspicion bias

Knowledge of a subject’s prior exposures or personal biases may influence both the process and the outcome of diagnostic tests.

Differential Reference bias

When not all participants receive the same reference test in a diagnostic accuracy study.

Hawthorne effect

When individuals modify an aspect of their behaviour in response to their awareness of being observed.

When a topic is fashionable (‘hot’) investigators may be less critical in their approach to their research, and investigators and editors may not be able to resist the temptation to publish the results.

Hypothetical bias

A distortion that arises when an individual’s stated behaviour or valuation differs to that of their real behaviour or valuation.

Immortal time bias

A distortion that modifies an association between an exposure and an outcome, caused when a cohort study is designed so that follow-up includes a period of time where participants in the exposed group cannot experience the outcome and are essentially ‘immortal’.

Catalogue of Bias

Confounding by indication

Data-dredging bias

Detection bias

Diagnostic access bias

Diagnostic suspicion bias

Differential Reference bias

Hawthorne effect

Hot stuff bias

Hypothetical bias

Immortal time bias

Incorporation bias

Industry Sponsorship bias

Information bias

Informed presence bias

Insensitive measure bias