Cohort Simulation
The process of running a Markov model by tracking the proportion of a hypothetical cohort in each health state over cycles, not individual patients.
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.
Cohort Trace
The complete record of the proportion of a modelled cohort occupying each health state at every cycle, produced by a Markov cohort model.
Common Random Numbers
A variance reduction technique using the same sequence of random numbers across simulations of different alternatives, reducing the variance of their difference.
Compartmental Model
A modelling approach dividing a population into distinct compartments, such as susceptible, infected, and recovered, and tracking flow between them over time.
Competing Risks
A situation where a person is at risk of more than one type of event, so one event's occurrence prevents another from ever happening.
Conditional Probability
The probability that an event will occur given that another specified event has already occurred, calculated from their joint probability.
Confidence Ellipse
A graphical region, typically on a cost-effectiveness plane, showing where the true joint value of incremental cost and effect is expected to fall.
Constant Hazard
A survival pattern where the instantaneous risk of an event stays the same at every point in time, matching an exponential distribution.
Constrained Optimisation
A mathematical approach to finding the best outcome, such as maximum health benefit, subject to limiting conditions, such as a fixed budget.
Contact Rate
A parameter in an infectious disease model representing how often individuals come into contact with one another in a way that could transmit infection.
Continuous Model
A mathematical model in which time or another key variable flows continuously rather than advancing in discrete steps.
Control Variates
A variance reduction technique exploiting a related quantity with known expected value to reduce the variance of the estimate actually wanted.
Convergence
The property of an iterative process, such as a Markov chain Monte Carlo run, settling into a stable pattern reflecting the target distribution.
Correlation
A statistical measure of how closely two variables move together, ranging from negative one to positive one.
Correlation Matrix
A table showing the pairwise statistical correlation between each pair of variables, used to represent how uncertain model parameters move together.
Cox Proportional Hazards
A widely used survival model estimating covariate effects, such as treatment, on the hazard rate while leaving the baseline hazard function unspecified.
Cox-Snell Residual
A residual used to check a survival model's overall fit, which should follow a standard exponential distribution if the fitted model is correct.
Cross-Validation
A statistical technique assessing how well a model generalises to independent data, typically by repeatedly splitting data into fitting and testing subsets.
Cumulative Hazard
The total accumulated risk of an event by a given point in time, found by integrating the instantaneous hazard rate up to that point.
Cure Fraction
The proportion of a population modelled as having no residual risk of the disease-specific event after successful treatment, effectively behaving as cured.