ABSTRACT
Meta-analysis has both strengths and weaknesses. A major strength is that it produces results based on large combined samples—sometimes very large samples. Such very large samples yield very reliable results. However, if the studies subjected to a meta-analysis have serious methodological flaws, then the mathematical synthesis of their results will also lack validity. An additional strength of meta-analysis is the objectivity of its conclusions. Note that in a traditional literature review, the conclusions are expressed in words. The phrasing, emphasis, and other characteristics of written communication are used to express the conclusions. The traditional review is not objective from a mathematical point of view. A potential weakness occurs if a researcher is not careful in the selection of studies to include in a meta-analysis. Poor selection might produce results that are difficult to interpret or meaningless. A final potential weakness of meta-analysis stems from what is known as publication bias.
