The existing literature in the field of social sciences has mainly employed either large-n statistical analyses or case studies as methods for testing its arguments. Due to the limitations of both the methods, many previous studies have not analyzed conjunctural causations adequately. Nevertheless, considering that the institutional factors come under research focus increasingly and they have discrete natures, it is necessary for us to pay more serious attention to conjunctural effects. As a method for exploring conjunctural causations, Qualitative Comparative Analysis (QCA) has come to be employed by an increasing number of studies. QCA, however, has been criticized for reasons such as its inability to include control variables and the dichotomization of variables. The purpose of this paper is to examine whether such criticism is valid, or whether the results obtained from QCA are, in fact, unreliable. I have used two methods-QCA and regression analysis-to analyze an empirical research question about countries' frequency in the use of quasi-judicial institution in the GATT/WTO. A comparison of the results will reveal the validity of QCA results and clarify the limitations of the regression analysis method. Reexamining the effects of the variables that were underemphasized in the regression analysis conducted by the previous studies would be fruitful agenda for future studies.