Meta-analysis
A study that statistically combines the results of multiple independent trials on the same question, generally considered stronger evidence than any single trial alone. Several of this site's studied-dose citations are meta-analyses covering dozens of underlying trials and thousands of participants.
Example
A 2013 meta-analysis of 19 randomized trials and 1,683 subjects (trial doses roughly 0.1-5mg) is the main citation behind the 0.5-5mg studied dose range we use for melatonin.