ABSTRACT
Meta-analysis provides a technique that allows researchers to aggregate data and summarize existing reports. The technique is used to reduce or eliminate various sources of artifact and statistical error. Additionally, meta-analysis provides an ability to examine the impact of various design issues and various theoretical possibilities. In this chapter, we explain what meta-analysis is and the justification for using the procedure. Our goal in this chapter is to enhance understanding of meta-analysis so that reading subsequent chapters is easier. The discussion does not consider a number of technical issues relating to the mathematical or methodological features of meta-analysis, as those discussions do exist and can be found in various textbooks dealing with meta-analysis (e.g., Cooper & Hedges, 1994; Hunter & Schmidt, 1990).
