Randomised controlled trials work on the principle of random allocation – that is, unbiased allocation means we can be confident that any observed differences between treatment groups are due to the treatments being examined rather than due to any inherent differences between the groups. The randomised controlled trial is widely regarded as the principal method for obtaining a reliable evaluation of treatment effectiveness of healthcare interventions. However, only those factors known to affect outcome should be considered. If the number of prognostic factors is large, then minimisation can be used to provide treatment balance as well as balance over these factors. This method eliminates the problem of predictability while maintaining balance across combinations of factors. This paper demonstrates that for most UK trialists the preferred method of randomisation is using permuted blocks of varying random length within strata. However, very few respondents considered that more complex methods offer any advantages. It was thought that groups should be balanced at baseline to avoid imbalance and help face-validity. Most trialists believed that simple randomisation is suitable for larger trials but there is a high probability of possible imbalance between treatment groups in small trials. Trialists reported using simple randomisation, permuted blocks and stratification more often than more complex methods such as minimisation. ![]() In this paper we describe the results of a survey of UK academics and publicly funded researchers to examine the extent of the use of various methods of randomisation in clinical trials. However, there is uncertainty as to which is the most preferred method of randomisation in any given setting and to what extent more complex methods are actually being implemented in the field. ![]() ![]() In healthcare research the randomised controlled trial is seen as the gold standard because it ensures selection bias is minimised.
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