An analysis by Professor Peter M Rothwell and his colleagues (Nuffield Department of Clinical Neuroscience, University of Oxford, UK) published in 2012 in the medical journal The Lancet (http://www.thelancet.com) assessed the effects of daily aspirin intake on cancer mortality. They looked at individual patient data from 51 randomized trials (77,000 participants) of daily intake of aspirin versus no aspirin or other anti-platelet agents.

According to the authors, aspirin reduced the incidence of cancer, with maximum benefit seen when the scheduled duration of trial treatment was five years or more and resulted in a relative reduction in cancer deaths of about 15% (562 cancer deaths in the aspirin group versus 664 cancer deaths in the control group). Specify the aspect of this study that pertains to

(a) design,

(b) description, and

(c) inference.