Abstract: Six features of user studies are presented and contrasted with the same features in another assessment method, usability evaluation. The connection between these assessment methods and the disciplines of research, engineering, and design is analysed. The three disciplines are presented in a timeline chart showing their inter-relationship with the final goal the creation of computing products. Background discussions explore three definitions of research as well as three methodologies for conducting research: experimental, observational, and correlational. It is demonstrated that a user study is an example of experimental research and that a usability evaluation is an example of observational research. In terms of the timeline, a user study is performed early (after research but before engineering and design), whereas a usability evaluation is performed late (after engineering and design but before product release).