Likert items and questionnaires are widely used in HCI, particularly to measure user experience. However, there is some confusion over which is the right test to use to analyse data arising from these instruments. Furthermore, this book has proposed several more modern alternatives to traditional statistical tests but there is little evidence if they are better in the context of this particular sort of data. This chapter therefore reports on several simulation studies to compare the variety of tests that can be used to analyse Likert item and questionnaire data. The results suggest that this sort of data best reveals dominance effects and therefore that tests of dominance are the most suitable, and most robust, tests to use.