Reporting the sample size calculation

A detailed statement of the basis of the sample size calculation should be included in the protocol and in the final report. This statement should contain the following  

Significance level to be used this will usually be 5 per cent and relate to a two-tailed test or 5 per cent depending on issues of multiplicity. 

The CONSORT statement (Moher et al. (2001)) sets down standards for the reporting of clinical trials and their recommendations in relation to the sample size calculation are in line with these points. 

There may, of course, be cases, especially in the early exploratory phase, where the sample size has been chosen on purely practical or feasibility grounds. This is perfectly acceptable in that context and the sample size section in the protocol should clearly state that this is the case. 

The following example is taken from a published clinical trial. 

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