You have to change the core code in "mod\feedback\analysis_to_excel.php". Around line no : 260 or 261, write a code that get all users including "non respondents".....and then write to excel file.
regards,
Brahmaiah Petluri
(Edited by Helen Foster to remove signature according to our moodle.org forums code of conduct - original submission Monday, 23 April 2012, 10:11 AM)