How do you analyze and process qualitative research data from large numbers of participants and websites? How can UX Research be used to inform broader best practices in design? In 2014, Google and AnswerLab collaborated to create data-driven design principles for the mobile web that have since been published and used extensively. This session will go in-depth on the unique tools and research methods that were employed in order to conduct 119 usability interviews in two cities encompassing 100 mobile websites. Attendees will learn best practices in conducting a large scale qualitative research study that included 4 sets of moderators and dataloggers and how the lead researchers were able to gather in-depth and timely insights across the whole dataset by approaching the data analysis phase as its own research study in order to develop the published principles.