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Table 1 How summary results of clinical trials can be misleading even when everyone gets the same relative risk reduction.

From: Assessing and reporting heterogeneity in treatment effects in clinical trials: a proposal

Assumption: Treatment reduces baseline risk by 25% without any treatment related harm
  Control Event Rate*
(CER, %)
Experimental Event Rate
(EER, %)
Relative Risk Reduction (RRR) Absolute Risk Reduction
(ARR)
Number Needed to Treat (NNT)
   (% of study population)      
Overall result (100%) 8 6 0.25 0.02 50
   Average risk subjects (75%) 4 3 0.25 0.01 100
   High risk subjects (25%) 20 15 0.25 0.05 20
  1. * See Appendix 1