Latent Class Model
A statistical model that assumes a population consists of unobserved subgroups with distinct preferences, estimating both each subgroup's traits and individual membership probability.
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.
Latent Growth Model
A latent growth model is a structural equation model treating each patient's starting level and rate of change in repeated health scores as latent factors.
Latent Transition Analysis
Latent transition analysis (LTA) is a longitudinal latent class method that estimates how patients move between unobserved health or behaviour states.
Latent Variable
A latent variable is an unobserved quantity, such as health-related quality of life or preference class membership, estimated from observed indicators.
Latin Hypercube Sampling
Latin hypercube sampling is a stratified Monte Carlo design that draws each input to a health economic model once from each of n equally likely intervals.
Law of Large Numbers
The law of large numbers says the average of independent patient costs or simulation draws settles on the true mean as more are added.
Least Squares Approximation
Least squares approximation estimates the coefficients of a chosen model by minimizing the sum of squared residuals between observed or target values and the corresponding model values.
Leave-One-Out
Leave-one-out cross-validation tests a cost or risk prediction model by refitting it without each observation in turn and predicting the one left out.
Left Censoring
Left censoring occurs when a patient's event, such as disease onset, is known only to have happened before the first observation, at an unknown time.
Left Truncation
Left truncation (delayed entry) occurs when people join a survival analysis risk set after time zero and are observed only if still event free at entry.
Leverage Point
A leverage point is an observation, such as one patient in a cost regression, whose predictor values lie far from the rest and can pull the fitted model.
Life Expectancy
Life expectancy is the average number of further years people of a given age would live under stated death rates, a core input to health economic models.
Life Table
A life table shows how many of an imagined group survive and die at each age under set death rates, giving survival and life expectancy for health models.
Life Table Method
The life table (actuarial) method estimates survival from deaths and withdrawals in fixed intervals, treating withdrawals as at risk for half an interval.
Life Years Gained
Life years gained (LYG) are the extra years of mean survival an intervention gives over its comparator, without quality adjustment, in economic evaluation.
Likelihood Ratio
A likelihood ratio is how many times as likely a test result or other evidence is under one hypothesis, such as having a disease, as under another.
Likelihood Ratio Test
The likelihood ratio test (LRT) compares nested models, such as Weibull and exponential survival curves, to judge whether extra parameters improve fit.
Lindahl Equilibrium
A Lindahl equilibrium is an equilibrium for a public good, such as disease surveillance, where personal prices equal marginal benefits and sum to its cost.
Linear Pool
The linear pool is a weighted average of several experts' probability distributions, giving one input distribution for a health economic model.
Linear Programming
Linear programming identifies the best feasible allocation of limited resources when the objective and constraints can be expressed as linear relationships.