Left Censoring
A form of censoring in which an event is known to have occurred before an observed time, but its exact prior timing is unknown.
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.
Life Table
A tabular record of a population's mortality experience, showing the probability of death at each age and the resulting survivors over time.
Life Table Method
A survival technique dividing follow-up into fixed intervals and calculating the proportion of at-risk patients surviving each, accounting for censoring.
Likelihood Ratio Test
A statistical test comparing the fit of two nested models by their ratio of likelihoods, used to judge whether added parameters improve fit.
Linear Model Health
A statistical or decision-analytic model in which inputs and outputs are related by a simple linear function, such as a constant per-unit cost.
Linear Pool
A method combining multiple experts' probability distributions by taking a weighted arithmetic average, producing a single pooled distribution.
Linear Programming Health
An optimisation technique identifying the resource allocation that maximises or minimises a linear objective subject to linear constraints, such as a fixed budget.
Log-Logistic Distribution
A probability distribution capable of representing a hazard function that first rises and then falls over time.
Log-Logistic Model
A survival model based on the log-logistic distribution, representing a hazard function that rises to a peak and then declines.
Log-Normal Distribution
A probability distribution in which the logarithm of the variable follows a normal distribution, often used for hazards that rise then fall.
Log-Normal Model
A survival model based on the log-normal distribution, capable of representing a hazard that rises then falls, similar in shape to log-logistic.
Log-Rank Test
A hypothesis test comparing survival distributions between groups by comparing observed and expected event counts at each event time.
Logarithmic Pool
A method combining multiple experts' probability distributions by taking a weighted geometric average rather than a simple arithmetic average.
Main Effect
The portion of output variance attributable to a single input parameter considered on its own, distinguished from its interaction effects with others.
Markov Assumption
The defining property of a Markov model that the probability of a future transition depends only on the current state, not on prior history.
Markov Chain
A mathematical sequence of states in which the probability of moving to any next state depends only on the current state.
Markov Chain Monte Carlo
A class of algorithms generating samples from a complex probability distribution by constructing a Markov chain that converges to that distribution.
Markov Cohort Model
A Markov model tracking a hypothetical cohort collectively as proportions across health states over cycles, rather than simulating each patient separately.
Markov Microsimulation
A Markov model simulating individual patients one at a time through their health state history, capturing heterogeneity a cohort model cannot represent.
Markov Model
A Markov model is a state-transition model in which a cohort or individuals move among mutually exclusive health states over repeated cycles, with future transitions determined by the current state under the model’s memory assumptions.