There are a number of advantages of this method of research:
o it is possible to obtain a complete response from different categories of a sample population
o more complex information can be collected
o it is more personal than the questionnaire and often produces better response rates
o the researcher may have more control over the question sequence and timing
o some questions can be adjusted in response to the answers given to other questions
o the researcher can explain some questions to the respondent in case of confusion, and thus can ensure that the responses given are more valid.