Final answer:
Interviews are best conducted in private to ensure that subjects feel safe and comfortable, which encourages them to provide honest and detailed responses, thereby enhancing the quality of the primary research.
Step-by-step explanation:
An interview is best conducted in private primarily because it allows the subject to open up and provide honest and detailed responses. Conducting interviews in private minimizes distractions and assures the subject that their privacy is protected, which can foster a more authentic and meaningful conversation. Given the nature of interviews as an investigative tool, they are a core aspect of primary research, where information is collected firsthand. Privacy ensures that the subject feels safe to disclose sensitive or in-depth information which is crucial for the accuracy and integrity of the research. Whether it's a face-to-face discussion or through phone or remote methods, the crux of an interview is the valuable back-and-forth exchange it facilitates between the interviewer and the interviewee.