A meta-analysis is a consolidation of similar studies on a single, well defined topic. The each study may have covered a variety of topics, but with the meta-analysis, each study will have addressed the common topic in depth and collected data regarding it.
The meta-analysis is a well-respected means of developing broad-based conclusions from a variety of studies. (I have included a book on the topic at the end of this article.) If you search the literature, you will note that meta-analyzes are often found in the medical literature, particularly in relationship to the effectiveness or problems with medications.
In some quarters, the meta-analysis is not always welcome or respected. Human factors (Human engineering) is rooted in experimental psychology, and meta-analyzes are not always respected or well-received in this community. It is work outside of the laboratory. It is not collecting your own data, but using the data collected by others, thus the tendency has been to consider the meta-analysis as lesser.
However, the meta-analysis has a particular strength in that it provides a richer and wider view than a single study with a single population sample. It is true that the studies of others often do not directly address all the issues that researchers could study if those researchers performed that research themselves. In other words, the level and the types of research related controls were employed by the researchers themselves. But, again, the meta-analysis can provide a richness and the numeric depth that a single study cannot provide.
Thus the question is, to use or not to use a meta-analysis when collecting data about a specific population? Should a meta-analysis be used in lieu of collecting empirical data?
Answer. There are no easy answers. Yes, a meta-analysis could be used in lieu of an empirical analysis, but only if there are enough applicable studies recently performed. However, I would suggest that when moving forward with a study of a specific, target population that the first response should be to initiate a literature search and perform some level of a meta-analysis. If the data is not available or is incomplete, then the meta-analysis will not suffice. But, a meta-analysis is always a good first step, and a relatively inexpensive first step, even if the decision is made to go forward with an empirical study. The meta-analysis will aid in the study's design and data analysis. And will act as a guide when drawing conclusions.