II. Definitions

  1. Hazard Rate
    1. First-time event frequency per unit of time (e.g. mortality rate)
  2. Hazard Ratio
    1. Frequency of an event or condition in an experimental group as compared with a control group over a specific period of time
      1. Hazard Ratio = (Exposed Hazard Rate) / (Control Hazard Rate)
    2. Typically the experimental group is exposed to an event, activity, medication or substance not shared with the control group
    3. Hazard Ratio <1 suggests a protective effect of the exposure (lower frequency than control group)
    4. Hazard Ratio >1 suggests a causative or provocative effect associated with the exposure (higher risk than control group)
    5. In contrast with Odds Ratio and Relative Risk, Hazard Ratios reflect an instantaneous ratio at a specific period in time (e.g. 5 year survival)

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