Generalizing from PRSA to public relations: How to accommodate sampling bias in public relations scholarship

One of the major challenges to conducting externally valid, quantitative scholarship in public relations is accessing samples of practitioners that are willing to participate in academic research. One sampling frame would naturally be the membership of the Public Relations Society of America (PRSA), which is the world's largest professional association for public relations practitioners. Yet, even if the question of access were resolved, there still remains the question of external validity, i.e., the issue of whether and to what extent the membership of PRSA (or any other sampling frame) reflects the population of public relations practitioners in general.