Cointervention
A cointervention (co-intervention) is a treatment other than the one under study that trial participants receive; unequal use across arms can bias results.
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.
Collinearity Diagnostics
Collinearity diagnostics are regression checks, such as variance inflation factors, showing when predictors overlap too much to estimate separate effects.
Common Comparator
A common comparator is a treatment, such as placebo or standard care, that two other treatments were each tested against, anchoring an indirect comparison.
Communality
Communality is the proportion of an observed variable's variance explained by the common factors in a factor analysis, the complement of its uniqueness.
Comparative Effectiveness Research
Comparative effectiveness research (CER) compares the benefits and harms of different health care options in routine care to show what works best for whom.
Composite Endpoint
A composite endpoint is a trial outcome combining two or more events, such as death or hospitalisation, usually counting a patient once at the first event.
Concurrent Control
A concurrent control is a control group drawn from the same population as the treated group and followed over the same period, so time trends affect both.
Condition Index
A condition index is the ratio of the largest singular value of a scaled regression design matrix to another singular value, used to assess near-linear dependence among predictors.
Confidence Interval
A confidence interval (CI) is a range around an estimate, such as a cost difference, built so a set share, often 95%, of such ranges hold the true value.
Confidence Interval Estimation
The statistical process of calculating a range of plausible values for an unknown parameter based on sample data and a specified confidence level.
Confidence Profile Method
The confidence profile method is a Bayesian method that adjusts studies of varied design for bias and pools them into parameter distributions for HTA.
Confirmatory Factor Analysis
Confirmatory factor analysis (CFA) tests whether data fit a prespecified model linking health questionnaire items to the latent factors they measure.
Confounder
A confounder is a variable, such as disease severity, that affects both the treatment a patient receives and the outcome, biasing unadjusted comparisons.
Confounding
Confounding is bias in an estimated treatment effect when a common cause of treatment and outcome mixes the treatment's effect with group differences.
Confounding by Aggregation
Confounding by aggregation is bias when group-level data, such as regional or trial averages, mix differences between groups into an exposure's effect.
Confounding by Indication
Confounding by indication is bias in observational treatment studies arising when the reason a patient is treated also affects their risk of the outcome.
Construct Validity
Construct validity is how well a PROM's scores fit hypotheses about it, covering structural validity, hypotheses testing and cross-cultural validity.
Contamination
Contamination occurs when trial participants receive the other arm's intervention, usually controls getting the new one, diluting the measured effect.
Content Validity
Content validity is how far a health measure's items are relevant, comprehensive and understood for its construct, target population and context of use.
Contingency Table
A contingency table counts observations cross-classified by two or more categorical variables, such as trial arm by outcome or test result by disease.