Transmission Probability
The likelihood that an infectious disease passes from an infected to a susceptible individual during a single contact between them.
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.
Trapezoidal Rule
A numerical integration technique approximating a definite integral by dividing the area under a curve into trapezoids and summing their areas.
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.
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-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.
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.
Unimodal Hazard
A hazard function that rises to a single peak and then declines over follow-up, rather than a monotonic or bathtub pattern.
Utility Weight
A numerical value representing the relative desirability of a specific health state, used to weight time in that state for QALYs.
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.
Variance Reduction
Statistical techniques, including antithetic variates and control variates, used to reduce a Monte Carlo simulation's statistical variability for a given number of iterations.
Variance-Based Sensitivity
Global sensitivity analysis techniques, including Sobol indices, decomposing total output variance into components attributable to each parameter and their interactions.
Variance-Covariance Matrix
A table showing each parameter's variance and the covariance between each pair, summarising both individual uncertainty and interdependence among model inputs.
VOI Analysis
An abbreviation for value of information analysis, applying formal decision-theoretic methods to quantify the expected benefit of reducing decision uncertainty.
Wald Test
A statistical test assessing whether an estimated parameter differs significantly from a specified value, based on the ratio of estimate to standard error.
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 class of tests comparing survival distributions using different weights at different follow-up times, including the log-rank, Peto, and Tarone-Ware tests.
Wilcoxon Test
A test comparing survival distributions that gives greater weight to earlier event times than later ones, unlike the standard log-rank test.