Records

Methodological context for: Elwood PC, Cochrane AL, Burr ML, Sweetnam PM, Williams G, Welsby E, Hughes SJ, Renton R (1974). A randomized controlled trial of acetyl salicylic acid in the secondary prevention of mortality from myocardial infarction. BMJ 1,436-440. and Boston Collaborative Drug Surveillance Group (1974). Regular aspirin intake and acute myocardial infarction. BMJ 1:440-443.

Allocation bias

Differences between the people compared

 

Unanticipated effects

Identifying unanticipated effects of treatments