Individual Patient Meta-Analysis
An evidence synthesis approach combining original patient-level records from multiple studies into one unified dataset, rather than only summary statistics.
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.
Informative Censoring
A form of censoring in which the reason observation ends is related to a participant's underlying risk, violating standard survival analysis assumptions.
Instrumental Variable
A variable associated with the exposure of interest but with no direct effect on the outcome except through that exposure, used to address confounding.
Instrumental Variable Analysis
A technique estimating a causal effect despite unmeasured confounding, using a variable that affects treatment but not the outcome except through treatment.
Intention-to-Treat Analysis
A method analysing trial data by original random treatment assignment, regardless of whether participants actually received or completed that treatment.
Inter-Rater Reliability
The degree of agreement between two or more independent observers assessing the same phenomenon, commonly quantified using a statistic such as Cohen's kappa.
Interim Analysis
A planned analysis of trial data conducted before final completion, typically to assess safety, efficacy, or futility and inform continuation decisions.
Internal Consistency Reliability
A measure of how well different items within an instrument, all meant to assess the same construct, produce correlated results.
Interquartile Range
A dispersion measure calculated as the difference between the seventy-fifth and twenty-fifth percentiles, the range containing the middle half of observations.
Interrupted Time Series
A quasi-experimental design analysing observations before and after an intervention, testing for a significant change in level or trend at that point.
Intra-Rater Reliability
The degree of agreement between repeated assessments made by the same rater evaluating the same phenomenon on separate occasions.
Intraclass Correlation
A measure quantifying the proportion of total variance in an outcome attributable to differences between groups or clusters, relative to variance within them.
Jackknife
A resampling technique estimating a statistic's variability by systematically recalculating it after removing one observation at a time.
Jackknife Standard Error
An estimate of a parameter's statistical uncertainty calculated using the jackknife technique of omitting one observation at a time and examining resulting variability.
K-Fold Cross-Validation
A technique assessing how well a model generalises by dividing data into equal folds, training on all but one and testing on the rest.
Kaiser Criterion
A factor analysis rule retaining only factors with an eigenvalue greater than one, since these explain more variance than a single original variable.
Kendall Tau
A non-parametric measure of association between two ranked variables, based on the number of concordant and discordant pairs of observations.
Kurtosis
A measure describing a distribution's tail shape relative to a normal distribution, higher values indicating heavier tails and more extreme outliers.
Last Observation Carried Forward
A missing data method substituting a participant's most recent value for all subsequent missing time points, assuming their condition stayed unchanged.
Latent Class Analysis
A technique identifying unobserved, categorical subgroups within a population from patterns of responses, assuming these fully explain the observed associations.