Root cause analysis (RCA) is a recommended practice in retrospectives and cause–effect diagram (CED) is a commonly recommended technique for RCA. Our objective is to evaluate whether CED improves the outcome and perceived utility of RCA. We conducted a controlled experiment with 11 student software project teams by using a single factor paired design resulting in a total of 22 experimental units. Two visualization techniques of underlying causes were compared: CED and a structural list of causes. We used the output of RCA, questionnaires, and group interviews to compare the two techniques. In our results, CED increased the total number of detected causes. CED also increased the links between causes, thus, suggesting more structured analysis of problems. Furthermore, the participants perceived that CED improved organizing and outlining the detected causes. The implication of our results is that using CED in the RCA of retrospectives is recommended, yet, not mandatory as the groups also performed well with the structural list. In addition to increased number of detected causes, CED is visually more attractive and preferred by retrospective participants, even though it is somewhat harder to read and requires specific software tools. 
Diagrams or structural lists in software project retrospectives – An experimental comparison