How do two meta-analyses of similar data reach opposite conclusions?

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Abstract
EDITOR—In their meta-analysis Fahey et al concluded that treatment with antibiotics made no significant difference to the resolution of acute cough,1 although they found a trend favouring antibiotics. The Cochrane meta-analysis on treatment of acute bronchitis concluded that antibiotics have a modest beneficial effect.2 Eight of the nine studies extracted were the same in both meta-analyses, and 90% of the 750 patients were used in both. How can two meta-analyses based on the same studies …