Is there a need to cite a general idea in the introduction which shall be later developed with a reference? Say like you state in your introduction the following:


  
    This part will examine the demographic reality and the cultural habits of X people in Y country.
  


In the body of your work, you elaborate with citations:


  
    X people are characterized by a habit of doing A, B and C (Smith 2010, p. 1). They are a population of 100000 (Smith 2010, p. 2), whatever.
  


Is it required to backup the introduction statement with the same citations? isn't it just a general statement? In case where the 'general statement' (which supposedly doesn't need citations) was inspired by the actual cited study, shouldn't I back it up even if written in a general form?

My question was inspired from this.
Citations are only needed when you make a statement that requires external justification.

Thus, if you say: "This paper will examine X people in Y country" there is no need for external justification, since it is a statement about the paper itself.

When you say "X people in Y country are characterized by a habit of doing A, B and C", however, that's a statement that requires justification, either by external citation or by data presented in the paper.