Ancillary Study
A supplementary study conducted alongside or within a primary study, often using the same participants or data, to address additional research questions beyond the original study design.
Glossary A–Z
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Attack Rate
A cumulative incidence measure used in outbreak settings.
Bias
Systematic error that distorts a study estimate.
Cohort Study
Study following exposed and unexposed groups over time.
Endemic
Constant presence of a disease in a region or population.
Epidemic
Occurrence of disease above expected levels in a community.
Incidence
Number of new cases in a population over a period.
Pandemic
Epidemic spread across multiple countries or continents.
Surveillance
Ongoing systematic collection and interpretation of health data.