And if you really want everything to be as anonymous as can be: in survey2 switch off everything that is shown on the tab "Notification & data management".
Even then a clever person could find out via the server logs what happened, but that is something more obscure. Maybe you can even switch off server logging. But I am not sure about that.
Even then a clever person could find out via the server logs what happened, but that is something more obscure. Maybe you can even switch off server logging. But I am not sure about that.