When in doubt, randomise
What are randomised trials and why are they important: one of a set of videos made for the 100th anniversary of the UK Medical Research Council
Also, a post about public randomisation ceremonies as a way of making the process transparent and obviously fair in trials where whole communities rather than individuals are randomised. In this case it was in Cameroon, but the PRISM trial of improved support for new mothers in Victoria, Australia used the same approach.
Thomas Lumley (@tslumley) is Professor of Biostatistics at the University of Auckland. His research interests include semiparametric models, survey sampling, statistical computing, foundations of statistics, and whatever methodological problems his medical collaborators come up with. He also blogs at Biased and Inefficient See all posts by Thomas Lumley »