This chapter, The Surgical Ethics of Numbers: Sample Size and Surgical Research by David L. Streiner, underscores that ideally, the number of participants in a study should be selected to ensure a statistically significant finding if, in fact, there truly is one. Unless this is determined a priori, however, it is possible that there may be either too many or, more commonly, too few participants. If there are too few, the study may be underpowered, meaning that there is a significant chance that the results will not be statistically significant, even if a difference indeed exists (Type II error). Conversely, having too many subjects may lead to trivial and clinically unimportant differences being deemed significant. Ethical issues arise in both situations. In the former case, patients might have been exposed to the risks of a new intervention; there would be expenditures of time, money, and effort that result in erroneous conclusions. Moreover, further research in that area may be hindered due to the negative results. With too many subjects, many participants in the experimental group would have faced unnecessary risks, the trial’s duration would have been extended, and resources would have been wasted without any added benefit. While these issues affect all medical research, surgical interventions often carry heightened immediate risks (e.g., complications, anesthesia) that magnify the moral obligation to determine sample size appropriately before enrolling patients.