I interview people a lot and I just do not understand how only a few people actually clarify questions before answering them. What usually happens then is that the interviewer has to put an extra effort into trying to make sure that she is not the confused one. The issue is that it also happens in a case of otherwise strong candidates.<p>How do you begin an interview to prevent that from happening?
There are many terrible interviewers and companies out there who would treat asking for clarification as a weakness so I imagine many interviewees avoid asking for clarification to avoid appearing "weak".<p>As others have said make sure you start the interview clearly inviting questions, but also if the candidate still seems reticent (they might believe it's a trick offer) maybe engage in a dialog as they start addressing the question.<p>For example immediately ask an open ended question about some edge case "What do we think should happen if the tree only has a single node?" or something like that. By immediately beginning a dialogue you invite more discussion. But bear in mind many candidates just won't enter into a discussion, it's not how they work, so try not to hold it against them if they are otherwise perfectly suited.
The interviewer should say something like (in a friendly tone) "we're not trying to catch you out. Please do ask for clarification if I haven't been clear with any of the questions", and start the interview with a discussion style question to allow a bit of chat back and forth between the candidate and interviewer, to tip it more into a conversation than an interrogation.