 By convention, this is what a 2x2 table looks like.
 Be sure to label the table correctly with exposure status on the side and disease status across the top.
 One tip I found was just draw some of these out as soon as you get your scratch paper.
 You may or may not need the totals depending on what you are trying to measure.
 Just remember to think carefully about what the question is asking. Also, don’t let a change in terms throw you. For instance, instead of sick and well, you might see died and lived.
FORMULAS:
 OR = (A/B) / (C/D)
 RR = (A / (A+B)) / (C / (C+D))
 Experimental Event Rate (EER) = a/a+b
 Control Event Rate (CER) = c/c+d
 Relative Risk Reduction (RRR) = CEREER/CER
 Absolute Risk Reduction (ARR) = CEREER
 Absolute Risk Increase (EERCER)
 Number Needed to Treat (NNT) = 1/ARR
 Number Needed to Harm (NNH) = 1/ARI


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