How do we Justify the " who, when, and where" conditional in the theoretical model?
There are several considerations in the process of addressing this question (Finding the Right Theory). For example, the area of knowledge we are dealing with is very important. In Physics, a researcher has a hunch and immediately tries to define a mathematical model to back it up, then later experiments will follow to link abstractions to reality. The original theory was a hunch or a hypothesis justified by limited prior knowledge and logic.
In applied areas such as business and IT management, the research question needs to be important in practice. Whichever accepted research models have been validated provide a strong guideline. If validated measures for the relevant constructs already exist, so much the easier. On the other hand, often new technologies or new ways for business innovation gets ahead of existing theories; new theories must be proposed, new measures must be developed.
I hope that helps.
Dear Amir Khushk the golden rule to find a suitable theory for a study is to read as much literature one can in his/her currently interested area of research. It will give a novel researcher the "hot" current topics in that research area and will help find effective theoretical foundations for a study. There is no right or wrong in selecting a theory in social science research if a researcher can justify his/her choice(s). TQ