An intriguing research area is difficult populations. A difficult population is one in which the participants refuse to respond to research efforts. This may be the refusal to complete a questionnaire in a quantitative study or refuse to engage in semi-structured interviews in a qualitative study. For example, doctors are notorious for not returning survey instruments, as are CEOs. Both populations are extremely busy with responsibility to patients and shareholders respectively. Another difficult population is illegal immigrants. Their fear of exposure prevents them from engaging in research projects.
What issues would you face if you were sampling a difficult population? How would you try to solicit responses or obtain an acceptable response rate? Finally how would you identify the difficult population issues if you were to present your findings to an audience?