Biostatistical expertise is required when the trial is designed, and must continue to be available as data are collected, analysed and prepared for the final report on the trial. Statistical considerations will govern the number of patients needed to obtain a significant result from the trial, the number of patients needed depending on the anticipated difference in the result between the treatment groups of the trial. The plan for the statistical analyses to be used at the conclusion of the trial must be determined in advance and specified within the protocol. When results are finally analysed, they should be presented in a form that facilitates clinical interpretation.