History of Meta-Analysis
Prior to the establishment of meta-analysis, researchers often summarized findings of various studies by grouping together similar aspects of the research. For example, if a researcher was reviewing literature regarding the effect of a reading program intervention, he or she may have stated that 15 of 25 studies showed that reading programs led to increases in student ACT scores. However, this method did not take into account the diverse designs and quality of the various research studies that were being summarized or the discrepancies in study results (Gay, Mills, & Airasian, 2009; Rubin & Babbie, 2008). Furthermore, the summarization approach resulted in subjective research, often varying from one researcher to the next due to inconsistent ways of selecting and analyzing such research (Gay, Mills, & Airasian). Introduced in the early 20th century (Moncrieff, 1998; Rosenthal & DiMatteo, 2001), meta-analysis initially was used primarily in clinical medical research (Nijkamp & Pepping, 1998). However, in the 1970’s, Glass, McGaw, and Smith (1981) adapted this method of research for the social sciences, and over the past 30 years, it has been widely applied to quantitative research in education, psychology (personal and industrial), criminology, and other social sciences (Bangert-Drowns & Lawrence, 1991; Duvall & Tweedie, 2000; Mann, 1994; Robey & Dalebout, 1998).