There are many challenges to be faced when conducting randomized controlled trials (RCTs) in pediatric research. One important challenge is the determination of an appropriate sample size. Recruiting more children than necessary risks unnecessary overexposure of children to an inferior treatment, whereas underestimating the sample required will lead to inconclusive or unreliable results. Both options pose important ethical dilemmas for the pediatric researcher.

Reviews have concluded that sample size calculations are frequently based on inaccurate assumptions regarding the key pieces of information needed.1,2 For example, a recent “failed” pediatric RCT highlighted the commonly encountered problem of underestimating the SD of a continuous primary outcome variable.3 This leads to underestimation of the necessary sample size, inadequate statistical power, and, consequently, an unanswered study question. Similarly, an incorrect estimation of the frequency with which a dichotomous outcome, or event, occurs in the control group of a trial (known...

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