Half-Life
The time required for a drug's concentration in the body to fall by half, a key parameter determining dosing frequency.
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.
Harrell C-Index
A survival model discrimination measure generalising the ROC area under curve to time-to-event data, the probability the model ranks patients correctly.
Hazard Function
A function describing the instantaneous risk of an event at a given point in time, conditional on having survived to that point.
Hazard Rate
The instantaneous probability of an event at a specific point in time, given survival without the event up to then, on a continuous scale.
Hazard-to-Probability Conversion
The mathematical transformation converting an instantaneous hazard rate into the probability of an event occurring over a specific discrete time interval.
Health Behaviour
An action or pattern of action that affects an individual's health, healthcare use or response to prevention and treatment.
Health Capital
The stock of health an individual holds at a given time, modelled as a durable asset that yields healthy time and depreciates with age.
Health Depreciation
The rate at which an individual's stock of health capital declines over time, generally assumed to accelerate with age.
Health Investment
Resources an individual or system devotes to maintaining or improving health capital, including healthcare use, exercise, and other health-promoting behaviour.
Health Production Function
A theoretical relationship describing how inputs such as healthcare, education, income, and lifestyle combine to produce health as an output.
Healthcare Production Function
A theoretical relationship describing how medical inputs, such as physician time, tests, and drugs, combine to produce healthcare services or outcomes.
Hedges' G
A standardised effect size measure similar to Cohen's d but corrected for small sample size bias.
Herd Immunity Threshold
The proportion of a population that must be immune to achieve herd immunity, mathematically related to a pathogen's basic reproduction number.
Hidden Markov Model
A statistical model in which the true underlying state cannot be directly observed, only indicated indirectly and probabilistically by observable data.
Hierarchical Model
A modelling approach representing nested data, such as patients within hospitals, allowing effects to vary at each level while borrowing statistical strength.
Hierarchical Testing
A multiple testing strategy organising hypotheses into a prespecified sequence, so later tests are only conducted if earlier, higher-priority tests succeed.
Hosmer-Lemeshow Test
A goodness of fit test assessing how well a logistic regression model's predicted probabilities match observed outcome frequencies across risk groups.
Human Capital Approach
A method for valuing productivity lost to illness, disability, or premature death, based on the market wages the person would otherwise have earned.
Hyperbolic Discounting
A pattern of time preference in which people discount the near future more steeply than the distant future, unlike constant exponential discounting.
Hypothesis Testing
A formal framework for evaluating whether observed data provide enough evidence to reject a null hypothesis in favour of an alternative.