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Document set current to 30 July 2026
Defined term · Statistics and inference

Absolute risk difference

The difference in event probability between arms. Depends on baseline risk and is the measure from which a number needed to treat is derived.

Document identifier
CEI-GT-069
Series
Defined term
Version
1.0
Published
30 Jul 2026
Last reviewed
30 Jul 2026
Certainty
Not rated

§1Absolute risk difference

§1.1Also known as

Risk difference

§1.2Category

Statistics and inference — Terms describing how effects are estimated and how uncertainty is expressed.

§1.3Related terms

  • Number needed to treat — The reciprocal of the absolute risk difference: the number of people who must be treated for the stated duration for one additional person to benefit. Rises sharply as…
  • Hazard ratio — The ratio of the instantaneous event rates in two arms, assumed constant over follow-up. A hazard ratio without an absolute risk difference does not convey how much…
Compound Evidence Institute · CEI-GT-069 · https://compoundevidence.com/glossary/absolute-risk-difference/ · retrieved 30 July 2026
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