I'd like first of all to express my appreciation of your help. Second, I can see why you feel it is a bit strange. This is primarily because the writers of the study at hand are not native speakers of English. They are two German researchers, who conducted a study about the ethics of PR in Germany. Every once in a while, I also get a taste of the strange and sometimes ambiguous things they write.
I don't know if an online study can be considered a field study. Maybe our dear colleagues can give us their opinions in this regard.
But the structure "occupational field" is one in use that means مجال مهنى . This is why I tend to agree with Dr. Oussama. If you are still not sure, maybe you can have a look at this link:
http://jobs.careers.org/topic/316-jobs-by-occupational-field
The translation workplace 
peer agreement (net): +4
