Time-Fixed Covariate
A patient characteristic in a survival model measured once and assumed constant throughout follow-up, such as baseline age or sex.
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.
Time-Homogeneous Model
A Markov model in which transition probabilities remain constant throughout the entire modelled time horizon, regardless of how many cycles have passed.
Time-Inhomogeneous Model
A Markov model in which transition probabilities are allowed to vary over the time horizon, such as mortality risk rising with age.
Time-to-Event
Outcome data recording the duration until a specific event of interest occurs, such as disease progression or death, possibly censored.
Time-to-Event Analysis
Statistical methods analysing data on the time until a specific event occurs, such as death, while appropriately handling censored observations.
Time-Varying Covariate
A patient characteristic in a survival model allowed to change value over follow-up, such as a repeatedly measured biomarker.
Time-Varying Hazard
A hazard rate that changes in magnitude over follow-up, unlike a constant hazard that stays the same at every point.
Tolerance Interval
An interval calculated to contain a specified proportion of an entire population's values with a given confidence, unlike a confidence or prediction interval.
Top-Down Costing
A costing method that starts from total observed expenditure for a programme and divides it by units delivered to produce an average unit cost.
Tornado Diagram
A horizontal bar chart displaying one-way sensitivity analysis results, bars ranked from largest to smallest range, resembling a tornado shape.
Total Effect Index
A variance-based sensitivity measure quantifying an input's total contribution to output variance, including its individual effect and all interactions with other inputs.
Trade-off
A situation in which achieving more of one objective requires accepting less of another, such as extra health benefit only at extra cost.
Trajectory Analysis
A statistical approach identifying and characterising distinct patterns of change in an outcome over time, often revealing subgroups with different courses.
Transient State
A health state within a Markov model that a patient can leave and potentially return to, unlike an absorbing state such as death.
Transition Matrix
A table giving the probability of moving from each health state to every other state within one Markov model cycle, each row summing to one.
Transition Probability
The likelihood that a patient in a given health state at a cycle's start will move to another state, or stay, by its end.
Transition Reward
A cost or outcome value applied at the moment a patient moves between two health states, unlike a state reward accrued over time.
Transmission Model
A model explicitly representing how an infectious disease spreads through a population by tracking interaction between infectious and susceptible individuals.
Transmission Probability
The likelihood that an infectious disease passes from an infected to a susceptible individual during a single contact between them.
Trapezoidal Rule
A numerical integration technique approximating a definite integral by dividing the area under a curve into trapezoids and summing their areas.