All the following statements concerning meta- analysis are true EXCEPT.
Meta-analyses combine results from several studies and, through statistical methods, calculate an overall estimate of effect. Ecological studies use data based on groups of people rather than individuals. Associations observed on an aggregate level may not represent associations on an individual level (ecological bias or ecological fallacy).
It is a study in which the units of analysis are populations or groups of people, rather than individuals.
It is used to enhance the statistical power of research findings where number in available studies are too small
It is applied by pooling results of small, randomized, controlled trials when no single trial has large enough numbers to reach statistical significance
It combines results from different studies to obtain a numerical estimate of an overall effect