Just a suggestion, if you don't get enough replies, perhaps you can open a thread in the "Services" subforum of bitcointalk and offer a small bitcoin incentive to fill out your survey. I'm sure that lots of people would participate if you did this. Good luck OP with your thesis!
Normally it shouldn't be a big problem to find enough people to help fill in a survey, especially for a graduate project.
If the only incentive is money it not really how it should be imo.
TS, good luck with your survey and thesis!
Yes, of course money shouldn't be the only incentive, but at the time of my reply, OP had 0 replies and no one had completed the survey. Glad to see him getting replies!
If you need even more replies OP, there are other sites as well where you can post such as reddit, hope you have all the info you need!