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Table 1 Calculating a number-needed-to-treat(NNT) from the results of a RCT.

From: Critical appraisal skills of family physicians in Ontario, Canada

A study looked at the effect of a cholesterol lowering drug in patients with coronary heart disease. One outcome the investigators looked at was all-cause mortality. 256 (11.5%) of the 2223 people in the placebo group died during the 5-year follow-up and 182 (8.2%) of the 2221 people in the treatment grouped died during the 5 years. The absolute risk reduction (ARR) was therefore 3.3% or 0.033.
What would the number-needed-to-treat (NNT) be in this case?
NNT = ______________