Critical appraisal is the process of judging the validity and quality of a research paper.
Major points to consider when appraising systematic reviews include:
Is the study valid?
What are the results, and are they significant?
Are the results applicable?
The PRISMA checklist is also helpful in identifying elements to look for in a systematic review, although it is not a quality instrument per se; the SPIRIT checklist likewise.
Greenhalgh, T. (1997). How to read a paper. The Medline database. BMJ, 315(7101), 180-3
Greenhalgh, T. (1997). How to read a paper. Getting your bearings (deciding what the paper is about). BMJ, 315(7102), 243-6
Greenhalgh, T. (1997). How to read a paper: Assessing the methodological quality of published papers. BMJ, 315(7103), 305-8
Greenhalgh, T. (1997). How to read a paper. statistics for the non-statistician. i: Different types of data need different statistical tests. BMJ, 315(7104), 364-6
Greenhalgh, T. (1997). How to read a paper. statistics for the non-statistician. ii: "significant" relations and their pitfalls. BMJ, 315(7105), 422-5
Greenhalgh, T. (1997). How to read a paper. papers that report drug trials. BMJ, 315(7106), 480-3
Greenhalgh, T. (1997). How to read a paper. papers that report diagnostic or screening tests. BMJ, 315(7107), 540-3
Greenhalgh, T. (1997). How to read a paper. papers that tell you what things cost (economic analyses). BMJ, 315(7108), 596-9
Greenhalgh, T. (1997). Papers that summarise other papers (systematic reviews and meta-analyses). BMJ, 315(7109), 672-5
Greenhalgh, T, & Taylor, R. (1997). Papers that go beyond numbers (qualitative research). BMJ, 315(7110), 740-3
Data extraction is the process of transcribing information from the primary studies under review to a standard form or template that has been designed to capture all of the detail relevant to the meta-analysis.
Double data extraction is preferred for accuracy - this is when two researchers extract the data independently and discuss any discrepancies or consult a moderator to arrive at consensus.