Simpson Method
A numerical integration technique approximating a definite integral by fitting a series of parabolic segments to the function, more accurate than linear approximation.
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Simpson Rule
A numerical integration technique approximating a definite integral by fitting a series of parabolic curves to the function being integrated.
Simulated Annealing
An optimisation technique modelled on slowly cooling metal, occasionally accepting worse solutions during search to avoid becoming trapped in a poor local solution.
Simulation Method
A general approach to estimating a model's results by repeatedly running it computationally, rather than solving for results using closed-form equations.
SIR Model
A basic epidemic model dividing a population into susceptible, infectious, and recovered compartments, representing flow between them using differential equations.
Sobol Indices
Variance-based global sensitivity measures decomposing a model's total output variance into portions attributable to each input parameter and their interactions.
Sobol Sequence
A method generating a sequence of points that fills a multidimensional space more evenly than simple random sampling, improving simulation efficiency.
Spline Model
A model using piecewise polynomial functions joined smoothly at knots to represent a flexible, non-linear relationship such as time and hazard.
Standardised Mortality Ratio Application
The use of a standardised mortality ratio to adjust survival estimates for background mortality within a health economic model.
State Occupancy
The amount of time, typically in cycles, that a patient or cohort proportion spends within a given health state in a Markov model.
State Reward
The cost or health outcome value assigned to a health state within a Markov model, accrued for each cycle a patient occupies it.
State Space Model
A modelling framework representing a system's evolution over time through a defined set of possible states and transition probabilities between them.
State Transition Model
A general term for a decision-analytic model, such as a Markov model, representing disease progression as movement between defined health states.
Statistical Fit
A measure of how well a specified statistical model's predictions align with observed data, judging whether the specification adequately fits the pattern.
Stochastic Analysis
An analysis in which a model incorporates randomness explicitly, so repeated runs under the same inputs can produce different results, unlike a deterministic model.
Stochastic Programming
An optimisation framework incorporating parameter uncertainty directly into the process, seeking a solution that performs well across possible parameter values.
Stock and Flow Model
A system dynamics structure representing accumulations, called stocks, such as infected individuals, and the rates of change into and out of them, called flows.
Stratified Log-Rank
A variant of the log-rank test accounting for stratifying variables, comparing survival within each stratum before combining into an overall statistic.
Stratified Sampling
A sampling technique dividing a population into distinct subgroups, called strata, and drawing a separate sample from each to ensure adequate representation.
Structural Sensitivity Analysis
A sensitivity analysis testing how results change under alternative structural assumptions, such as a different survival extrapolation function, rather than parameter values.