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First- and Second-Generation Antipsychotics for Children and Young Adults

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Modes of Results Reporting and Statistical Analysis in the Comparative Effectiveness Review (2 of 2)

Absolute Risk Difference: The absolute value of the mathematical difference between the rates (risk) of an event in the treatment and comparison groups.

  • ARD = |ARC-ART |

Number Needed to Treat or Harm (NNT, NNH): The number of patients to be treated to observe benefit or harm in one patient more than seen in the comparison group. The number of patients to be treated in order to find a benefit or harm attributable to the intervention.

  • NNT or NNH = |ARC-ART |-1 for a benefit or adverse event, respectively
  • Number of attributable events per 1000 = 1000 x | ARC-ART |