The goals influence the approach used for the study.
GOOD EVALUATION
Establishing convincing arguments for your design solution
By conducting complementary and regular evaluations at different stages of your design process using the appropriate evaluation methods (e.g. summative, formative, expert-based, observational, ...)
Evaluations should result in insights regarding possible problems and their causes in order to support refinement of your design specification
Look at user experience in its full breadth: Effectiveness, efficiency, satisfaction, learnability, mood, connectedness, ...
