Absolute Risk
The probability that an individual in a defined population will experience a specific outcome over a given period, without reference to a comparison.
Encyclopaedia
Explore comprehensive, evidence-informed explanations of key health economics concepts, including their development, application and relationships to other concepts. Published entries are validated through human expert review.
Concepts, entries and ontology terms
A concept page is a published entry on the wiki. Some concepts also have a full encyclopaedia article. The Health Economics Ontology (HEO) holds every concept, including dictionary terms without an article, so it is larger than the list of published pages. The knowledge graph shows how concepts relate to each other.
Absolute Risk Reduction
Absolute risk reduction (ARR) is the control group's risk of an outcome minus the treated group's risk over the same period, so ARR equals CER minus EER.
Accelerated Failure Time Model
An accelerated failure time (AFT) model is a survival model in which treatment or another factor stretches or shrinks time to an event by a time ratio.
Active Control Trial
An active control trial is a randomised trial testing a new treatment against a known effective treatment, not placebo, for superiority or non-inferiority.
Activity Limitation
Activity limitation is a difficulty a person has in carrying out a task or action, such as walking, washing or communicating, as defined in the WHO ICF.
Adaptive Trial Design
Adaptive trial design is a trial plan whose prespecified rules let interim data change the trial, such as stopping early, while keeping inference valid.
Additive Interaction Scale
The additive interaction scale judges two exposures to interact when their joint risk difference departs from the sum of their separate risk differences.
Administrative Censoring
Administrative censoring is right censoring that occurs when a trial's planned end of follow-up or data cut-off arrives before a patient has the event.
Administrative Data
Administrative data are records made to run or pay for care, such as claims, hospital admissions and prescriptions, reused to measure costs and outcomes.
Adverse Drug Reaction
An adverse drug reaction (ADR) is a noxious, unintended response to a medicine, where a causal link to the drug is at least a reasonable possibility.
Aggregate Data Meta-Analysis
Aggregate data meta-analysis pools study-level summary results, such as effect estimates and standard errors, from several studies into one estimate.
Allocation Concealment
Allocation concealment hides the next assignment in a randomised trial from recruiters until allocation, protecting the treatment effects that inform HTA.
Alpha Spending
Alpha spending is a group sequential trial method that spreads the type I error rate (alpha) across interim and final analyses as information accrues.
Analysis Error
Analysis error is a mistake in specifying, coding or reporting a statistical or economic analysis, such as a model slip that alters an ICER.
Analytic Epidemiology
Analytic epidemiology tests causes of disease by comparing groups, estimating the relative risks and attributable fractions used in economic models.
Anchoring Bias in Elicitation
Anchoring bias in elicitation is an expert's insufficient adjustment from a starting value, giving shifted, too-narrow distributions for model inputs.
Area Under Curve
Area under the curve (AUC), or C-statistic, is the probability a test or risk model scores a random case above a random non-case (0.5 chance, 1 perfect).
Asymptotic Normality
Asymptotic normality means an estimator's sampling distribution is approximately normal in large samples, the basis of Wald confidence intervals.
Attack Rate
Attack rate is the proportion of an at-risk population that develops the disease during an outbreak or other defined period: a risk, not a true rate.
Attributable Fraction
The attributable fraction is the share of cases, in the exposed or a whole population, that would not occur without an exposure, used to apportion burden.