Some limiting factors in meta-analysis.

In first explicating the notion of quantitative literature review for the social sciences, Glass (1976) argued that knowledge is not built from any individual study, but from the integration of findings from many studies. Individual studies do not so much yield knowledge as evidence with which knowledge can be built. Knowledge is socially constructed. To overemphasize a single study’s findings or integrate research only impressionistically leaves researchers knowing less than the evidence offers, insufficiently exploiting the wealth of data scattered in separate studies.