Value-Based Purchasing
Value-based purchasing is when a health purchaser ties provider payment or contracts to measured quality and outcomes, as in Medicare's hospital programme.
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.
Variance
Variance is the average squared deviation from the mean, measuring spread in patient costs and outcomes and the uncertainty of health economic estimates.
Variance Inflation Factor
The variance inflation factor (VIF) measures how much overlap among predictors enlarges a regression coefficient's variance in cost or outcome models.
Variance Reduction
Variance reduction is the use of simulation sampling or estimator design to lower Monte Carlo error for a specified quantity without changing the quantity being estimated.
Variance-Based Sensitivity
Variance-based sensitivity analysis apportions the variance of a health economic model output to each uncertain input and to their interactions.
Variance-Covariance Matrix
A symmetric array of variances and pairwise covariances that describes the scale and joint movement of a set of random quantities or estimates.
Variation
Variation is the spread of a measured quantity, such as cost, service use or outcome, across patients, providers, areas or time periods in a health system.
Varimax Rotation
Varimax rotation is an orthogonal factor rotation maximising the variance of squared loadings in each factor, used to find health questionnaire domains.
Vector Database
A vector database is a database that stores embeddings and returns the items nearest a query vector, used to search guidance and trial text by meaning.
Verification Bias
Verification bias is error in estimated sensitivity and specificity when who receives the reference standard, or which one, depends on the test result.
Vertical Equity
Vertical equity is the principle that those in greater need should get appropriately more care, and those more able to pay should pay more.
Visual Analogue Scale
The visual analogue scale (VAS) is a line, usually scored 0 to 100, on which people rate their own health or a health state between two labelled ends.
VOI Analysis
VOI analysis (value of information analysis) takes a model's PSA through EVPI, EVPPI, EVSI and ENBS in turn to decide if more research is worth its cost.
Wald Test
The Wald test checks whether model parameters, such as cost or risk regression coefficients, differ from hypothesised values given their standard errors.
Weak Dominance
Weak dominance is when another option costs no more and is at least as effective, and is strictly better on one, so the dominated option is dropped.
Web Ontology Language
Web Ontology Language (OWL) is a W3C standard ontology language whose formal logic lets software check and infer links between health economic concepts.
Weibull Distribution
A flexible probability distribution capable of a monotonically increasing or decreasing hazard rate depending on its shape parameter.
Weibull Model
A survival model based on the Weibull distribution, representing an increasing or decreasing hazard over time, though restricted to a monotonic pattern.
Weighted Least Squares Regression
Weighted least squares (WLS) is regression that weights each squared residual, ideally by the inverse of its error variance, as in meta-analysis for HTA.
Weighted Log-Rank
A survival-curve comparison test that weights each event-time observed-minus-expected count to emphasize a prespecified pattern of differences over follow-up.