Appraise  Strength of inference  Finding articles
Adverse Outcome Yes 
Adverse Outcome No 

Exposed Yes  a  b 
Exposed No  c  d 
RCT or Prospective cohort studies:
Casecontrol studies:
Confounding variable is one whose influence distorts the true relationship between a potential risk factor and the clinical outcome of interest.
Number Needed to Treat (NNT) The number of patients that need to
be treated with a specified therapy in order to prevent one additional bad
outcome. Calculated as the inverse of the absolute risk reduction
(1/ARR)
Absolute Risk Reduction (ARR) is the difference in risk
between the control group (X) and the treatment group (Y). ARR =
XY
Control Event Rate (CER)
The proportion of patients
in the control group who experience the studied event.
Experimental
Event Rate (EER)
The proportion of patients in the experimental
treatment group who are observed to experience the outcome of interest.
Relative Risk Reduction (RRR) is the percent reduction in risk
in the treated group (Y) compared to the control group (X). RRR = 1RR x
100%
PubMed:
From: Guyatt, G. Users' Guides to the Medical Literature: Essentials of Evidencebased Clinical Practice. AMA Press, 2002 and Strauss. EvidenceBased Medicine. How to Practice and Teach EBM. ChurchillLivingstone, 3rd edition, 2005 (pocket cards).
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