Quiz 3

Observational Study

A type of epidemiological study where researchers observe and analyze possible associations between exposures and outcomes.

Study Validity

The degree to which the conclusions drawn from a study are warranted, taking into account factors such as representativeness of the study sample, study methods, and extraneous factors that may impact the results.

Internal Validity

The extent to which differences in outcomes between groups in a study can be attributed to the effects of the exposure or intervention being investigated, and not due to random error, bias, or confounding.

External Validity

The ability to extrapolate study results from a sample population to a target population, ensuring that the findings are applicable to a broader context.

Random Error

Non-systematic error that leads to false associations between exposure and disease due to chance, with no assignable cause. It includes sampling error, which occurs when the sample collected is not representative of the target population.

Systematic Error

Error introduced by the study process that is distinct from random error. It includes selection bias, information/observation bias, and confounding, which can distort the relationship between exposure and disease.

Selection Bias

Bias resulting from an error committed by the investigator in the design or conduct of the study that leads to a false association between exposure and disease. It can occur in both the selection and retention of study subjects.

Information/Observation Bias

Bias in epidemiology that is different from the common definition, referring to ignorance or poor decision making by the investigator. It can result in incorrect or invalid estimates of the measure of association in a study.

Control Selection Bias

Bias that occurs in a case-control study when controls are selected from a hospital population that is already sick, leading to a distortion of the exposure-disease association.

Differential Surveillance

Different referral patterns or diagnosis based on exposure history, which can introduce bias in a study. An example is the risk of venous thromboembolism among oral contraceptive users, where different referral patterns may influence the association between exposure and outcome.

Loss to Follow-up

When participants in a study are lost during the follow-up period, it can reduce the power of the study and bias the results, leading to over or underestimation of the relationship between exposure and outcome.