Treatment Effect Heterogeneity
Variation in the size or direction of a treatment's effect across different patients, so a trial's average effect may not fit any one person.
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.
Truncation Error
The error introduced by approximating a mathematical process using a finite number of terms or steps.
Tunnel State
A modelling technique creating temporary, time-specific states a patient passes through in sequence, letting a Markov model approximate time-dependent risk.
Two-Tailed Test
A hypothesis test assessing evidence for an effect in either direction, without specifying in advance whether it is expected to be better or worse.
Two-Way Sensitivity Analysis
An analysis varying two parameters together across a grid of combinations, typically shown as a contour plot or heat map of results.
Type I Error
In hypothesis testing, the error of incorrectly rejecting a true null hypothesis, concluding a genuine effect exists when it does not.
Type II Error
In hypothesis testing, the error of failing to reject a false null hypothesis, concluding no effect exists when a genuine effect is present.
Unbiasedness
A property of an estimator whose expected value, across repeated samples, equals the true underlying value of the parameter being estimated.
Uncertainty Quantification
The formal process of measuring how much confidence should be placed in a model's results, given the sources of uncertainty affecting it.
Uniform Distribution
A probability distribution in which every value within a defined range is equally likely to occur.
Unimodal Hazard
A hazard function that rises to a single peak and then declines over follow-up, rather than a monotonic or bathtub pattern.
Unstructured Correlation
A correlation structure for repeated measures allowing the correlation between every pair of time points to be estimated freely and independently.
Utility Function
A mathematical representation of preferences that assigns a numerical value to each possible outcome, so higher-utility outcomes are preferred.
Utility Maximisation
The behavioural assumption that individuals make choices intended to achieve the highest possible satisfaction given their preferences and constraints.
Utility Weight
A numerical value representing the relative desirability of a specific health state, used to weight time in that state for QALYs.
Vaccine Effectiveness
The degree to which a vaccine reduces disease risk under real-world conditions in a general population, unlike efficacy measured under trial conditions.
Vaccine Efficacy
The degree to which a vaccine reduces disease risk among vaccinated individuals under the controlled conditions of a clinical trial.
Value of Information
A framework quantifying the expected benefit of reducing decision uncertainty, comparing expected outcomes under current uncertainty against outcomes if it were resolved.
Value of Information Analysis
The application of value of information methods to a health economic decision, typically used to judge whether further research is worth conducting.
Value of Statistical Life
A monetary estimate of the value society places on reducing the risk of death, derived from willingness to pay for a small risk reduction.