Publication bias in clinical trials due to statistical significance or direction of trial results

Most Cochrane reviews provide knowledge on the effects of healthcare interventions. But some, Cochrane methodology reviews, tackle issues relevant to the methods for the evaluation of health care. Sally Hopewell, along with a team of reviewers from England, Scotland, Ireland, Norway and the USA, have prepared one such review and Sue Mallet from the Centre for Statistics in Medicine in Oxford, England, spoke to her about it.