Number needed to treat

doi:10.1136/bmj.b2493

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John Fletcher, clinical epidemiologist

¹BMJ, London WC1H 9JR

jfletcher{at}bmj.com

Two weeks after entry to a trial of antibiotics to treat symptoms of chest infection, 25% of people receiving placebo and 15% of people receiving antibiotics still had symptoms. What is the number needed to treat in this trial for antibiotics to cure symptoms at two weeks?