Cluster Randomization
A randomisation technique in which entire groups, such as clinics, rather than individuals, are randomly assigned to different treatment conditions.
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.
Cohen's D
A standardised measure of effect size expressing the difference between two group means in units of their pooled standard deviation.
Cohort Design
An observational design following a group sharing a common starting characteristic forward in time to observe a subsequent outcome of interest.
Communality
In factor analysis, the proportion of a variable's total variance explained by the underlying common factors, distinct from variance specific to it alone.
Condition Index
A diagnostic detecting problematic collinearity among predictor variables, calculated from the eigenvalues of the predictor matrix, larger values meaning worse collinearity.
Confidence Interval
A range of values, calculated from sample data, expected to contain the true population parameter with a specified level of confidence.
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.
Confirmatory Factor Analysis
A technique testing whether a hypothesised factor structure adequately explains observed correlations among measured variables, unlike exploratory factor analysis.
Construct Validity
The degree to which an instrument actually captures the underlying theoretical concept it is meant to measure, judged against theoretical expectations.
Convergent Validity
A form of construct validity shown when an instrument's scores correlate strongly with scores from other established instruments measuring a related concept.
Cook's Distance
A regression diagnostic identifying observations with disproportionately large influence on estimated coefficients, based on how much fitted values would change if removed.
Copas Model
A statistical model adjusting a meta-analysis result for potential publication bias by modelling how publication likelihood depends on results.
Correlation Coefficient
A measure quantifying the strength and direction of the linear relationship between two variables, ranging from negative one to positive one.
Credible Interval
A range of values, calculated within a Bayesian framework, believed to contain a parameter's true value with a specified posterior probability.
Credible Interval Estimation
The Bayesian process of calculating a range of plausible values for a parameter based on its estimated posterior probability distribution.
Criterion Validity
The degree to which an instrument's scores correlate with an accepted external reference measure, either concurrently or in predicting a future outcome.
Critical Value
The specific threshold of a test statistic separating the region where a null hypothesis is rejected from where it is not.
Cross-Sectional Design
An observational design measuring exposure and outcome simultaneously in a population at a single point in time, rather than over time.
Crossover Design
A trial design in which each participant receives more than one treatment being compared, typically in random sequence separated by a washout period.
Crossover Trial
A trial in which participants sequentially receive two or more treatments under comparison, with each participant's response compared against their own.