The scope of the study explains the extent to which your research area will be explored, and the parameters the study will operate. It gives the reader and the writer an insight into what the study is aimed at and what should be anticipated.
This implies that the scope of the study should define the purpose of your study, the sample size and qualities, geographical location, the timeframe at which the study will be executed, theories the study will focus on, etc.
The scope of the study is just an aspect of research writing, and great attention needs to be taken not to go beyond what is expected. Therefore, the scope of the study sheds light on areas your study will cover and what it focuses on. What your study area is not going to focus on is of no relevance to your research study, and the scope of the study eliminates that.