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.
Absolute Risk Reduction
The arithmetic difference between the absolute risk of an outcome in a control group and in a treatment group.
Accelerated Failure Time
A class of survival models assuming covariates act multiplicatively on time itself, speeding or slowing progression to an event, unlike a Cox model.
Accuracy
A general measure of how closely a test result, measurement, or prediction corresponds to the true underlying value, covering sensitivity and specificity.
Adaptive Study Design
A study design allowing prospectively planned modifications, such as changes in sample size, based on accumulating data without undermining its validity.
Adaptive Trial Design
A trial design incorporating prospectively planned opportunities to modify the trial, such as stopping early, based on interim data analysis.
Administrative Censoring
A form of right censoring occurring because a study reaches its planned end date before every participant has experienced the event of interest.
Aggregate Data Meta-Analysis
A technique combining summary results, such as reported means or event rates, from multiple studies into a single pooled estimate.
Alpha Spending
A group sequential trial method allocating the overall acceptable risk of a false positive across multiple planned interim analyses.
Area Under Curve
A summary statistic representing a predictive model's discriminative ability, the area beneath its ROC curve, from 0.5 for chance to 1 for perfect.
Asymptotic Normality
A statistical property whereby, as sample size grows large, an estimator's sampling distribution approaches a normal distribution regardless of the original data's shape.
Attack Rate
A measure of disease incidence in a specific outbreak, the proportion of an at-risk population that develops the disease over the outbreak period.
Attack Rate Ratio
A measure comparing the attack rate of a disease between two groups within an outbreak, such as those exposed and unexposed to a source.
Attributable Fraction
The proportion of disease cases within a population that would not have occurred without a specific exposure, showing its public health impact.
Attributable Risk
The difference in risk of an outcome between an exposed group and an unexposed group, the portion attributable to the exposure itself.
Autoregressive Correlation
A statistical structure describing how repeated measurements on the same individual are correlated over time, closer measurements typically more strongly correlated.
Average Treatment Effect
The mean difference in outcomes that would occur if every member of a population received a treatment versus a comparator instead.
Basic Reproduction Number
The average number of secondary infections produced by one infected person in a fully susceptible population with no interventions in place.
Basket Trial
A trial design evaluating a single treatment, often targeting a specific genetic marker, across multiple disease types simultaneously, rather than one disease.
Bayes Theorem
A mathematical formula describing how to update the probability of a hypothesis based on new evidence, combining a prior probability with a likelihood.