Intention-to-Treat Analysis
Intention-to-treat analysis compares outcomes and costs by randomised group, whatever treatment was received, estimating the effect of offering treatment.
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.
Concepts, entries and ontology terms
A concept page is a published entry on the wiki. Some concepts also have a full encyclopaedia article. The Health Economics Ontology (HEO) holds every concept, including dictionary terms without an article, so it is larger than the list of published pages. The knowledge graph shows how concepts relate to each other.
Interaction Effect
An interaction effect is the part of two factors' joint effect on a health outcome or model result that adding their separate effects does not explain.
Interest Rate
An interest rate is the price of borrowing money, a yearly percentage of the loan, and a benchmark weighed in setting health appraisal discount rates.
Interim Analysis
An interim analysis compares the arms of a clinical trial before it formally ends, to decide whether to stop it early for benefit, harm or futility.
Internal Consistency Reliability
Internal consistency reliability is how strongly the items in one health questionnaire scale agree with each other, usually measured by Cronbach's alpha.
International Comparison
International comparison analyses health spending, prices and outcomes across countries to judge health system performance and learn policy lessons.
Interpersonal Comparison of Utility
An interpersonal comparison of utility is a value judgement comparing the welfare levels or gains of different people, as summing QALYs or pounds does.
Interpolation
Interpolation estimates a value between observed or modelled data points using an assumed relationship across the interval.
Interquartile Range
The interquartile range (IQR) is the gap between the 25th and 75th percentiles, the spread of the middle half of data such as skewed patient costs.
Interrupted Time Series
Interrupted time series (ITS) is a quasi-experimental design tracking an outcome before and after a health policy to estimate changes in level and trend.
Interval Censoring
Interval censoring occurs when a patient's event time, such as disease progression, is known only to lie between two assessments, such as two trial scans.
Interval Scaling
Interval scaling means equal score differences reflect equal differences in health or preference, with an arbitrary zero, so ratios of scores mean nothing.
Intervention
An intervention is any test, treatment, programme, strategy or policy aimed at health or care; HTA compares its costs and effects with alternatives.
Interviewer Bias
Interviewer bias is systematic error caused by how an interviewer asks questions or behaves, as in time trade-off or willingness-to-pay surveys.
Intraclass Correlation
The intraclass correlation (ICC) is the share of variance in a health outcome lying between patients or clusters, used to judge reliability and clustering.
Investigational Device Exemption
An investigational device exemption (IDE) is a US FDA permit to test an unapproved medical device in a clinical study, often to support premarket approval.
Jackknife
The jackknife is a resampling method that recomputes an estimate, such as mean cost, leaving out each observation in turn to gauge bias and standard error.
Joint Model
A joint model fits a repeatedly measured biomarker and time to an event such as death together, so survival estimates for economic models reflect the link.
K-Fold Cross-Validation
An internal validation procedure that repeatedly fits a model on all but one of K data folds and evaluates it on the held-out fold.
K10
K10 is the ten-item Kessler scale, a non-preference-based measure of psychological distress used in population surveys and mental health trials.