A questionnaire is a research instrument consisting of a series of questions and other prompts for the purpose of gathering information from respondents. Interview Schedule is also used as a method of data collection but in this case, the data is collected by an interviewer rather than through a self-administered questionnaire. Interviewers read the questions exactly as they appear on the survey questionnaire. The choice of answers to the questions is often fixed (close-ended) in advance, though open-ended questions can also be included within a structured interview.
A questionnaire is self administered while interview involves face to face interaction of interviewer and respondent
So the questions remain the same for both interview and questionnaire?