- David J Torgerson, senior research fellowa,
- Marion K Campbell, senior statistician
- a Centre for Health Economics, University of York, York YO1 5DD
- b Health Services Research Unit, University of Aberdeen, Aberdeen AB25 2ZD
- Correspondence to: Dr Torgerson
This is one of an occasional series of notes on economics
In an earlier note we showed how economic criteria can help in sample size calculations by defining clinical endpoints of economic importance.1 However, there is a further issue concerning sample size calculations where economic information may be useful—the randomisation ratio.
Most randomised trials allocate equal numbers of patients to experimental and control groups. 2 3 This is the most statistically efficient randomisation ratio as it maximises statistical power for a given total sample size. However, this may not be the most economically efficient randomisation ratio.4 When two or more treatments under evaluation have a cost difference it may be more economically efficient to randomise fewer …