The correct answer is in-depth interviews
In-depth interviews are a qualitative technique that allows one or more themes to be explored, with greater depth than the common face-to-face interviews, since the objective of the latter is essentially to quantify, and the questions asked must follow a line that allows this end, either with closed questions or open or semi-open questions that allow for later coding.
With this qualitative technique, although there is an interview guide, it is not closed, and the interviewer, according to his experience and the conversation with the interviewee, can adapt the guide as a result of his interpretation, according to a established and critical dialogue with reality. Being a qualitative technique, the attempt to "understand" and / or "explain" a certain phenomenon or reality are the main reasons for its use.
In-depth interviews, as in all qualitative techniques, require a great deal of experience from the interviewers, since they only have a guiding thread for the interview; interviewers can manage the interview flow and the questions themselves. And they also require a great deal of experience from the analysts in order to turn the collected data into structured information and because they are subject to the subjectivity of the analysis. In this type of methodology, the interviewer and the analyst, when they are not the same person, work closely.