Biases | Catalog of Bias

Adherence bias

A systematic distortion in outcome data that arises when participants who adhere to a study protocol or intervention differ from those who do not adhere, when that difference relates to the outcome of interest.

Admission rate bias

Arises when the variables under study are affected by the selection of hospitalized subjects leading to a bias between the exposure and the disease under study.

All’s well literature bias

Occurs when publications omit or play down controversies or disparate results.

Allocation bias

Systematic difference in how participants are assigned to comparison groups in a clinical trial.

Apprehension bias

When a study participant responds differently due to being observed

Ascertainment bias

Systematic differences in the identification of individuals included in a study or distortion in the collection of data in a study.

Attrition bias

Unequal loss of participants from study groups in a trial.

Availability bias

A distortion that arises from the use of information which is most readily available, rather than that which is necessarily most representative.

Biases of rhetoric

An argument used to persuade the reader without appealing to reason or evidence.

Centripetal bias

The reputations of certain clinicians and institutions cause individuals with specific disorders or exposures to gravitate toward them.

Chronological bias

When study participants allocated earlier to an intervention or a group are subject to different exposures or are at a different risk from participants who are recruited later.

Collider bias

A distortion that modifies an association between an exposure and outcome, caused by attempts to control for a common effect of the exposure and outcome

Compliance bias

Participants compliant with an intervention differ in some way from those not compliant which can systematically affect the outcome of interest.

[NOTE: as of 18 July 2023 this bias has been superseded by Adherence bias. A detailed explanation is given here]

Confirmation bias

The search for and use of information to support an individual’s ideas, beliefs or hypotheses.

Confounding

A distortion that modifies an association between an exposure and an outcome because a factor is independently associated with the exposure and the outcome.