The role of research ethics committees in addressing optimism in sample size calculations: a meta-epidemiological study

Optimism in sample size calculations is common, but the influence of REC feedback on reducing overestimation appears limited. As this was a small, descriptive study from a single Dutch REC in 2015-2018, findings may not generalise to other settings or more recent practice. Future research should validate these findings and may help identify characteristics associated with overestimation, supporting RECs in recognising trials at risk of being underpowered.