Q: How to write the rationale or justification of a study?

Detailed Question -

How to  write the need of the study?

1 Answer to this question

The term used to imply why the study was needed in the first place is "rationale for research" or "rationale of a study." It is also sometimes referred to as the justification of the study. I have edited your question to reflect this. 

The rationale of a study is a very important part of the manuscript. You can do a thorough literature review to understand what is already known in your field of study and thereby identify the gaps in knowledge or the problems that are yet to be solved. Such gaps will form the framework of your study and outline the need for a new study.

Thus, in the Introduction section, you will need to provide a background on the topic and what is known on the topic. The next paragraph would indicate the gaps in the current literature and then lead to the goal/objective/rationale for your new study. 

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