SeriesAllocation concealment in randomised trials: defending against deciphering
Section snippets
Allocation concealment
Researchers have many misconceptions with respect to allocation concealment. Proper allocation concealment secures strict implementation of a random allocation sequence without foreknowledge of treatment assignments. Allocation concealment refers to the technique used to implement the sequence,4 not to generate it. Nevertheless, some people discuss allocation concealment with digressions into flipping coins or use of random number tables. Those digressions amount to methodological
Baseline comparisons
Although randomisation eliminates systematic bias, it does not necessarily produce perfectly balanced groups with respect to prognostic factors. Differences due to chance remain in the intervention groups—ie, chance maldistribution. Statistical tests, however, account for these chance differences. The process of randomisation underlies significance testing and is independent of prognostic factors, known and unknown.31
Nevertheless, researchers should present distributions of baseline
Conclusion
Proper randomisation remains the only way to avoid selection and confounding biases. The crucial unbiased nature of randomised controlled trials paradoxically coincides with their most vexing implementation problems. Randomised controlled trials antagonise human beings by frustrating their clinical inclinations. Thus, many involved with trials will be tempted to undermine randomisation, if afforded the opportunity to decipher assignments. To minimise the effect of this human tendency, trialists
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