It is no wonder that you look for an easy path to access your interviewees. More often than not, you will be overwhelmed by an irresistible feeling to select those people whom you know very well such as your friends, colleagues, students, and the like. The easier the access, the more labyrinthine the interview.
Interviewing whom you supervise
It is natural that you will have conflicts with your juniors at job. For instance, if you are a boss of a company along with a doctoral student, you organised an interview with your employees to know about their attitude and perception toward HR policies. You might think that you have rapport with your employees, so it will not be arduous for them to speak openly. However, one of the principles of establishing an equitable interviewing relationship is respondents will never make them unduly vulnerable by participating in an interview. You have a power of hiring and sacking your employees, and this they know very well. Consequently, this will restrict them discuss issues toward HR policies frankly.
Interviewing your students
Interviewing your own students is also not going to contribute constructively to your research. For instance, if you interview your own students to understand the effectiveness of a teaching method, your students will hardly be open to you. They know that how powerful you can be while assessing their performance in a class and assigning marks. So you should seek to interview other students who have been taught by other tutors with the same teaching method.
Sometimes you may choose your participants whom you know but not related to the subject area of your research. For instance, suppose you are going to have your participant to discuss the complexities that they face while teaching them English as another language. Instead of choosing a participant whom you know professionally, you choose the one whom you have met at a grocery shop or church. Considering a church relationship instead of interviewing relationship will limit the potential of the interview.
You may opt for participants to organise an interview because you have a great friendship with them, but interviewing relationship in such cases can be affected by friendship. Since you and participants know each other because of friendship, chances are you will not ask them to explore assumptions and seek clarity in events, and they will be assuming you understand what is being said. Further, you and participants can take lots of things for granted that does not happen when you have enough distance from your respondents.
So take effort to bring on a steady success to your research. Take a step forward outside your comfort zone to lend your research an increased reliability, validity and ethics.