On the Similarity of Web Measurements Under Different Experimental Setups

Measurement studies are essential for research and industry alike better understand the Web's inner workings and help quantify specific phenomena. Performing such studies is demanding due to the dynamic nature and size of the Web. Designing and setting up an experiment is a complex task, and many factors might affect the results. However, while several works have independently observed differences in the outcome of an experiment (e.g., the number of observed trackers) based on the measurement setup, it is unclear what causes such deviations. This work investigates the reasons for these differences by visiting 1.7M webpages with five different measurement setups. Based on this investigation, we build 'dependency trees' for each page and cross-compare the nodes in the trees. The results show that the measured trees differ considerably, that the cause of differences can be attributed to specific nodes, and that even identical measurement setups can produce different results.