Relationship of primary and secondary studies

<p>In the life sciences of medicine and psychology, studies are divided into primary studies (individual studies) and secondary studies. Secondary research includes - in ascending hierarchy - systematic reviews, meta-analyses and umbrella reviews. Systematic reviews provide a summary of existing studies, including an assessment of the current state of knowledge. In meta-analyses, a mean effect is calculated from the effects of the studies. An umbrella review, in turn, summarises several meta-analyses.</p>