Proportional Hazards Assumption
The Cox model assumption that the hazard ratio between two groups stays constant over follow-up, even as the absolute hazard rate changes.
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.
Pseudo-Random Number
A number generated by a deterministic algorithm that approximates the statistical properties of true randomness, used because genuine randomness is hard to compute.
Quartile
A descriptive statistic dividing a ranked dataset into four equal-sized groups, marking the twenty-fifth, fiftieth, and seventy-fifth percentiles.
Queuing Model
A mathematical model describing how entities wait in line for limited servers, used to analyse average waiting time and server utilisation.
Quick Ratio
A financial ratio calculated as current assets excluding inventory, divided by current liabilities, a more conservative liquidity measure than the current ratio.
Random Effects
In a mixed effects model, the components representing how individual units, such as patients, vary around an overall average relationship.
Random Number Generation
The computational process of producing a sequence of numbers approximating true randomness, used to sample parameter values in probabilistic health economic models.
Random Parameter Model
A discrete choice model that lets preference parameters vary randomly across individuals according to a specified distribution, rather than assuming identical preferences.
Range
A dispersion measure calculated as the difference between the maximum and minimum values in a dataset, sensitive to extreme outliers.
Rate-to-Probability Conversion
The mathematical transformation converting a continuous-time hazard rate into the probability of an event occurring within a discrete time interval.
Reference Case
A reference case is a documented set of preferred methodological choices that an institution asks analysts to follow so economic evaluations are transparent, consistent and comparable for a defined decision context.
Regression Analysis
Statistical techniques modelling the relationship between one or more predictor variables and an outcome variable, from simple linear to survival regression.
Relative Dose Intensity
A measure comparing the dose intensity a patient actually received to the originally planned, full dose intensity, expressed as a percentage.
Relative Error
The absolute error expressed as a proportion or percentage of the true or accepted value.
Relative Survival
A survival measure comparing observed survival in a population to expected survival in a comparable general population, without needing cause-of-death data.
Relative Survival Model
A statistical model estimating disease-specific survival by comparing observed survival against expected general population survival, without individual cause-of-death data.
Repeated Measures Analysis
A statistical approach analysing data in which the same outcome has been measured multiple times on the same individuals, accounting for correlation.
Residual
The difference between an observed value and the value predicted for it by a fitted statistical model.
Residual Analysis
A statistical technique examining the differences between a model's predicted values and observed data, checking for systematic patterns left unexplained.
Response Surface
A fitted mathematical approximation describing how a model's output varies with its inputs, built from limited runs and used to predict untested combinations.