Evidence Synthesis in the Social Sciences

Article screening generally takes place in stages - title and abstract screening, followed by full text - and best practice is that at least two independent reviewers should screen all studies.  The purpose of screening is to remove studies that are not ultimately related to your topic.  Researchers use their pre-defined inclusion/exclusion criteria to screen the titles/abstracts.  Those studies that pass through the title/abstract screening are then obtained in full text and screened again to decide whether the study will be included in the analysis.  If reviewers disagree on whether studies should be included, at any stage in the process, disagreements can be resolved by consensus or via an expert third party (though this should be laid out ahead of time in the protocol).