If there is group of individuals and we have standardized questionnaire with permission from author now the group is unable to complete the questionnaire.can the questionnaire be converted into interview for data collection.
By conversion into an interview, do you mean changing the existing items into open-ended questions for what would essentially be a qualitative interview?
No not making any changes as the group is unable to fill the questionnaire because of having disabilities mildly retarded so just to ask the same questions in the form of interview
If this is included in the methodology from the beginning , it can be piloted and compared with the self reported questionnaire , and if comparable results then seems OK to carry on