Transmission Model
A transmission model is an infectious disease model in which infection risk depends on how many people are infectious, so evaluations count herd effects.
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.
Trapezoidal Rule
The trapezoidal rule approximates a definite integral by replacing a curve with straight-line segments and summing the resulting trapezoid areas.
Treatment Sequence Model
A treatment sequence model is a decision model comparing ordered pathways of therapies, moving patients to the next line when a treatment fails or stops.
Tunnel State
A tunnel state is one of a fixed sequence of one-cycle temporary states in a Markov model, letting risks, costs or utilities vary with time in a state.
Two-Way Sensitivity Analysis
Two-way sensitivity analysis varies two inputs of a health economic model together over a grid of values to show which combinations change the decision.
Uncertainty
Uncertainty in health economics is imperfect knowledge of a model's true inputs, structure or methods, so the option chosen as best may prove to be wrong.
Uncertainty Quantification
Uncertainty quantification (UQ) measures how uncertainty in a health economic model's inputs and structure carries into its costs, QALYs and decision.
Unimodal Hazard
A unimodal hazard is an event rate that rises to a single peak and then falls, as log-logistic and log-normal survival models allow in HTA.
Value of Information
Value of information (VOI) analysis estimates the expected benefit of reducing decision uncertainty, to judge whether more research is worth its cost.
Variance Reduction
Variance reduction is the use of simulation sampling or estimator design to lower Monte Carlo error for a specified quantity without changing the quantity being estimated.
Variance-Based Sensitivity
Variance-based sensitivity analysis apportions the variance of a health economic model output to each uncertain input and to their interactions.
Variance-Covariance Matrix
A symmetric array of variances and pairwise covariances that describes the scale and joint movement of a set of random quantities or estimates.
VOI Analysis
VOI analysis (value of information analysis) takes a model's PSA through EVPI, EVPPI, EVSI and ENBS in turn to decide if more research is worth its cost.
Wald Test
The Wald test checks whether model parameters, such as cost or risk regression coefficients, differ from hypothesised values given their standard errors.
Weibull Distribution
A flexible probability distribution capable of a monotonically increasing or decreasing hazard rate depending on its shape parameter.
Weibull Model
A survival model based on the Weibull distribution, representing an increasing or decreasing hazard over time, though restricted to a monotonic pattern.
Weighted Log-Rank
A survival-curve comparison test that weights each event-time observed-minus-expected count to emphasize a prespecified pattern of differences over follow-up.
Wilcoxon Test
The Wilcoxon test in survival analysis, or Gehan-Breslow test, compares survival curves by weighting each event time by the number still at risk.