Conclusions
We sought to address one of the most crucial clinical question in contemporary clinical research: how large of an effect size is large enough to circumvent the need for further RCTs testing by the regulatory agencies? Our results suggest that drug developers can use the change in one logarithm of effect size as a benchmark to decide if further testing in RCTs should be pursued, or as a guide to interpreting the results reported in non-randomized studies. Further research would be helpful to better characterize the threshold of effect size above which testing in RCTs is not needed.