Being aware of the type of methodology used in a study is an important part of the research process. Many indexes -- such as PsycINFO -- provide limits to restrict your search results by methodology type.
A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Further further reading on the differences between systematic reviews and meta-analyses, see Garg et al.'s "Systematic Review and Meta-analysis: When One Study Is Just not Enough" CJASN January 2008, vol. 3 no. 1, 253-260.
For definitions of each methodology, visit the following APA Databases Methodology Field Values webpage.
For the purposes of MIR-850, Dr. Lilius has provided a list of research methodology types, arranged in descending order of strength. To summarize, the more meta-analyses and systematic reviews you identify to support your case, the better.
In the library session you will be shown how to limit your searches to include only results that adopted a particular methodology.