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Table 2 Reporting items for the protocol and report of a two parallel group superiority trial

From: Specifying the target difference in the primary outcome for a randomised controlled trial: guidance for researchers

Item no. Item description Protocol Report
1 State any divergence from the conventional approach.
2 State the primary outcome (and any other outcome which the study sample size calculation is based upon), or state why there is not one.
3 Reference the formula and/or simulation approach if the standard binary, continuous or survival outcome formulas are not used [2,11]. The primary analysis should be stated in the statistical analysis section.  
4 State the values used for statistical parameters (such as significance level and power).
5 State the underlying basis for determining the target difference:  
a. an important difference as judged by a stakeholder,
b. a realistic difference based upon current knowledge or
c. both an important and realistic difference.
6 Express the target difference according to the outcome type:
a. Binary: state the target difference as an absolute and/or relative effect, along with the intervention and control group proportions. If both an absolute and a relative difference are provided, clarify if either takes primacy in terms of the sample size calculation.
b. Continuous: state the target mean difference on the natural scale, the common SD and standardised effect size (mean difference/SD). It is preferable to also provide the anticipated control group mean even though it is not required for the sample size calculation.
c. Time-to-event (survival): state the target difference as an absolute and/or relative difference, provide the control group event proportion, along with the intervention and control group survival distributions. Additionally, the planned length of follow-up should be stated along with the assumed accrual pattern. If both an absolute and a relative difference are provided, clarify if either takes primacy in terms of the sample size calculation.
7 Explain the choice of target difference: specify and reference any formal method used or relevant previous research.  
8 State the sample size based upon the assumptions specified above (for a time-to-event outcome, the number of events required should also be stated). If any factors are incorporated which alter the required sample size (such as allowance for loss-to-follow-up) they should also be specified along with the final sample size.
9 Reference the trial protocol