Comparative Evaluation of Hierarchy Browsers

The field of information visualisation has seen tremendous growth over the last decade, with many new methods and approaches presented in the literature. However, evaluations of these new techniques are still rather scarce. This thesis presents a comparative evaluation of four visualisations of hierarchies: TreeView, Information Pyramids, TreeMap, and Hyperbolic Browser. The visualisations are implemented in Java as part of the Hierarchical Visualisation System (HVS), developed at Graz University of Technology. A semi-automated testing environment, The Hierarchical Visualisation Testing Environment (HVTE), was built upon HVS to simplify the running of a series of usability tests and to automate the collection of performance data. HVTE automatically provides participants with tasks in the sequence corresponding to their randomly assigned test case. Task completion times as well as typed answers are collected in a database. A counterbalanced, repeated measures study was designed to compare the four visualisations, with 32 test users each performing 8 tasks. The results showed almost no significant differences in task completion times between the four visualisations. The participants significantly preferred the TreeView in subjective ratings. All participants were familiar with this kind of visualisation and had years of experience working with it. The TreeMap visualisation performed quite well, but was rather unpopular in the subjective ratings. The Pyramids and Hyperbolic visualisations were rated in the middle.