Cumulative Incidence
The proportion of an initially disease-free population that develops a specific outcome over a defined follow-up period, a measure of average risk.
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.
Decile
A descriptive statistic dividing a ranked dataset into ten equal-sized groups, the first decile being the bottom ten percent and the tenth the top.
Decision Curve Analysis
A method evaluating a diagnostic or prognostic model's clinical value by calculating its net benefit across a range of possible intervention thresholds.
Delayed Entry
A survival analysis situation in which an individual is only observed from some point later than a common natural starting point, such as diagnosis.
Delta Adjustment
A sensitivity analysis technique shifting the assumed outcome for patients with missing trial data by a specified amount to test conclusions' robustness.
Delta Method
A statistical technique approximating the variance of a function of random variables using a Taylor series expansion, used for ratios such as the ICER.
Dependent Censoring
A survival analysis situation in which the reason for censoring is related to a participant's underlying risk of the event, violating standard assumptions.
Design Effect
A statistic quantifying how much a complex survey or clustered study's variance differs from what a simple random sample of the same size would give.
DFBETAS
A standardised version of the DFBETA diagnostic, scaled by its standard error, allowing influence of observations to be compared consistently across models.
Diagnostic Accuracy
The overall ability of a diagnostic test to correctly classify individuals as having or not having a condition, summarised using sensitivity and specificity.
Difference-in-Differences
A quasi-experimental technique estimating a policy's causal effect by comparing the change in outcomes over time between an exposed and a comparable unexposed group.
Discriminant Validity
A form of construct validity shown when an instrument's scores do not correlate strongly with measures of theoretically distinct, unrelated concepts.
Effect Size
A quantitative measure of a phenomenon's magnitude, such as the difference between two groups, expressed to allow comparison across studies using different scales.
Effect Size Estimation
The statistical process of calculating a quantitative measure of a treatment effect's magnitude, often standardised to allow comparison across differing measurement scales.
Effective Reproduction Number
The average number of secondary infections from one infected person in a population not entirely susceptible, accounting for existing immunity or control measures.
Effective Sample Size
The sample size a simple random sample would need to match the precision of an actual sample from a more complex design, such as clustered.
Egger Test
A statistical test for funnel plot asymmetry, and by extension potential publication bias, using regression of effect estimates against standard errors.
Eigenvalue
A mathematical quantity indicating the amount of variance explained by its corresponding direction, used in factor analysis to decide how many factors to keep.
Equivalence Trial
A trial designed to show a new treatment's effect is neither substantially better nor worse than an existing treatment, within a set margin.
Event-Free Survival
A time-to-event outcome measured from treatment start until any of a predefined set of significant events, such as progression or death, whichever comes first.