As explained by the British Journal of Obstetrics & Gynecology (and countless other scientific journals), randomized controlled trials (RCTs) are the “gold standard” for research because they provide “a rigorous tool to examine cause-effect,” which “is not possible with any other study design.” RCTs are studies in which people are randomly assigned to receive or not receive a certain treatment. This can mean anything from a drug or welfare benefit to a face mask or educational opportunity. Because RCTs are vastly more reliable than other types of studies, the World Health Organization adopted a “general principle” to “not review observational studies or simulation studies” if RCTs are available. Like any study, an RCT can be erroneous if it is poorly designed or executed. Keys to identifying such problems are provided at the first link below.