The purpose of this paper is to illustrate how a quantitative literature review or research synthesis can be used to aggregate information in the item response theory literature to address specific research questions. The research questions focused on the magnitude of the contribution of the number of items and number of examinees to the accuracy of parameter estimates in the two-parameter item response theory model. The results from 7 studies used in the research synthesis suggest that more than 63% of the variables in a commonly used indicator of parameter estimation accuracy was attributable to these 2 factors, and that this result holds across a variety of factors. Other questions that a research synthesis might be used to address in the item response theory literature are described. (Contains 13 tables and 31 references.) (Author/SLD)