Absolute Error
The absolute difference between an estimated or measured value and the true or accepted value.
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.
Absolute Risk
The probability that an individual in a defined population will experience a specific outcome over a given period, without reference to a comparison.
Absolute Risk Reduction
The arithmetic difference between the absolute risk of an outcome in a control group and in a treatment group.
Absolute Shortfall
A measure of disease severity calculated as the difference between the quality-adjusted life expectancy of a healthy comparator population and that of untreated patients.
Absorbing State
A health state within a Markov model from which no further transitions are possible, most commonly death, once entered permanently.
Accelerated Failure Time
A class of survival models assuming covariates act multiplicatively on time itself, speeding or slowing progression to an event, unlike a Cox model.
Accuracy
A general measure of how closely a test result, measurement, or prediction corresponds to the true underlying value, covering sensitivity and specificity.
Active Choice
A choice architecture approach requiring an individual to make an explicit selection rather than passively accepting a default.
Activity-Based Costing
A costing method that assigns overhead and indirect costs to services based on the actual activities that consume resources, rather than a simple volume measure.
Actuarial Analysis
The application of statistical methods to assess and quantify financial risk, such as the expected future cost of insurance claims.
Actuarial Method
A technique estimating survival probabilities by dividing follow-up into fixed intervals and calculating the proportion surviving each, accounting for those lost to follow-up.
Actuarial Projection
An estimate of future events, such as mortality, morbidity, or claims costs, based on statistical analysis of historical data patterns.
Actuarial Value
A measure representing the percentage of average healthcare costs a health plan is expected to cover for a standard population.
Adaptive Study Design
A study design allowing prospectively planned modifications, such as changes in sample size, based on accumulating data without undermining its validity.
Adaptive Trial Design
A trial design incorporating prospectively planned opportunities to modify the trial, such as stopping early, based on interim data analysis.
Adjustment Factor
A numerical multiplier applied to a base payment rate to account for specific circumstances affecting the cost of care, such as geographic wage differences.
Administrative Censoring
A form of right censoring occurring because a study reaches its planned end date before every participant has experienced the event of interest.
Administrative Cost Ratio
A measure of the proportion of an insurer's revenue spent on administrative functions, such as claims processing, rather than actual claims.
Adverse Event Rate
A measure of how frequently patients experience unintended harm from medical care, rather than their underlying condition, within a defined population.
Adverse Selection
Adverse selection occurs when people use private information about their risk before an agreement to make participation or contract choices, causing those who select into a market or plan to differ systematically from the wider population.