What are the advantages and disadvantages of open-end questions in either a written survey or a personal interview?

What will be an ideal response?

Open-end questions allow the respondent to provide a broad range of input and not be restricted to a defined set of response options. This is an advantage since it is possible to tap into the true feelings of the respondent and to obtain responses that might not have been anticipated when the survey was developed. The disadvantage is that analysis of the responses to open-end questions is difficult. The analyst must somehow code the potentially broad range of responses into categories. This takes time and often requires interpretation that might interject bias into the analysis.