Interviews.

In survey research, data collection instruments can be administered either as questionnaires in which there is no intervention between the data collection instrument and the subject or as an interview conducted by a human being. The intervention of a human interviewer between the survey instrument and the subject's responses has both advantages and disadvantages. In particular, interviewer bias and interviewer effects can impact the quality of the data obtained from the subject. However, interviewing techniques—in particular, cognitive interviewing that employs probing or "think aloud" methodologies—can improve the quality of the data gathered in a survey. These methods also help survey designers develop better survey instruments and help researchers better understand and predict human behavior. When properly used, interviewing techniques can give researchers both a depth and breadth of information that cannot be gathered through other data collection techniques.