The scope of the study (the tasks and questions)

The scope is a difficult subject to tackle because stakeholders very often want to use a usability study to cover everything at once, and the UX researcher will have to scale the expectations down to a feasible scope. The scope is constrained by what can reasonably be asked of the participants within the timeframe of the study. A video-based remote usability study will have a different test duration than a survey-based one, for example. The budget also influences the timeframe, and subsequently, the scope. 

The goal will determine whether the study's scope should comprise the entire product, only certain functions of it, or even just individual screens. If the goal is to determine the usability status quo of a product, for example, then the scope will encompass the entire product, whereas comparing three design alternatives...