They generally use small samples and also conduct direct one to one personal interviews. A detailed background is provided by the respondents and elaborate data concerning the respondents opinions, values, motivation, expression, feeling etc are obtained. Even their non-verbal expressions are observed. They take long time, therefore lengthy observations are involved.
These are conducted to customize individual responses. The questions will depend on what kind of answers are given. Even interview climate influences the respondents. The success of interviews depends on the rapport of the interviewers established with the respondents.