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  1. Carl Counsell
  1. University of Aberdeen, Department of Medicine & Therapeutics, Polwarth Building, Foresterhill, Aberdeen, UK; E-mail: cec{at}


Meta-analysis is the statistical technique by which data from a number of independent studies of the same topic are combined in order to determine the best estimate of the overall result from those studies. It can be applied to most types of epidemiological study (e.g. observational or case-control studies) but is most often used to combine the results of randomised controlled trials within the context of a systematic review (i.e. a review which outlines its methods to minimize bias and chance). A systematic review that includes a meta-analysis is often called a quantitative systematic review whereas one that does not may be called qualitative.

The main advantages of a meta-analysis are:

  • to increase the amount of data and so minimize the play of chance in producing spurious results (either false positive or false negative results);

  • to reduce over-emphasis on the results of a single study which may be

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