Growth Mixture Model
An extension of growth curve modelling allowing unobserved subgroups to follow qualitatively different average trajectories, rather than varying only in degree.
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.
Harrell C-Index
A survival model discrimination measure generalising the ROC area under curve to time-to-event data, the probability the model ranks patients correctly.
Hazard Ratio
A measure comparing the instantaneous risk of an event in one group relative to another, commonly estimated using a Cox model.
Hedges' G
A standardised effect size measure similar to Cohen's d but corrected for small sample size bias.
Heterogeneity Assessment
A statistical evaluation of how much effect estimates vary across studies in a meta-analysis, commonly quantified using the I-squared statistic.
Heterogeneous Treatment Effect
Variation in the size or direction of a treatment's effect across individuals or subgroups, so the overall average may not fit any one patient.
Hierarchical Model
A modelling approach representing nested data, such as patients within hospitals, allowing effects to vary at each level while borrowing statistical strength.
Hierarchical Testing
A multiple testing strategy organising hypotheses into a prespecified sequence, so later tests are only conducted if earlier, higher-priority tests succeed.
Hosmer-Lemeshow Test
A goodness of fit test assessing how well a logistic regression model's predicted probabilities match observed outcome frequencies across risk groups.
Hypothesis Testing
A formal framework for evaluating whether observed data provide enough evidence to reject a null hypothesis in favour of an alternative.
I-Squared
A statistic quantifying the percentage of total variation across studies in a meta-analysis attributable to genuine heterogeneity rather than chance.
Immortal Time
A period of follow-up during which, due to how exposure groups were defined, a participant could not possibly have experienced the outcome.
Imputation
A technique replacing missing data values with estimated substitutes, ranging from simple mean substitution to sophisticated multiple imputation approaches.
Incidence
The number of new cases of a disease occurring within a defined population over a specified period, unlike prevalence, which counts existing cases.
Incidence Rate
A measure of disease frequency calculated as new cases divided by total person-time at risk observed, accounting for varying follow-up lengths.
Incidence Rate Ratio
A measure comparing the incidence rate of an outcome between two groups, accounting for differences in total person-time at risk.
Independent Censoring
A form of censoring in which the reason observation ends is unrelated to a participant's underlying risk, satisfying standard survival analysis assumptions.
Indirect Comparison
A method estimating the relative effect of two treatments never studied against each other directly, using their separate effects versus a shared comparator.
Indirect Treatment Comparison
A method estimating the relative effect of two treatments never directly compared, typically via a common comparator both have been separately tested against.
Individual Patient Data Meta-Analysis
A meta-analysis obtaining and analysing original patient-level data from each study, rather than relying only on published summary results.