Structured interviews have a highly controlled format, while unstructured interviews have a relatively relaxed format. Semi-structured interviews fall in between, with a somewhat flexible format. The format of the interview depends on the type of information the interviewer is looking for, and the format he feels most comfortable using. Both structured and semi-structured interviews are valuable tools for finding the best candidate.
Level of Planning
In a structured interview, the interviewer comes prepared with a set list of questions to address. In a semi-structured interview, she has questions prepared, but she does not follow a strict agenda. The discussion may veer from the list of questions, and she may think of new ones during the discussion. However, if the discussion strays off topic or hasn't addressed specific topics she wishes to cover, she'll redirect the focus. Due to the low emphasis on planning, a semi-structured interview has a conversational feel.
In semi-structured interviews, the candidate often plays a large role in controlling the pace of the interview than he would in a structured interview. He has more opportunity to ask questions during the substance of the interview, or to offer information that the interviewer has not yet requested. In a structured interview, the interviewer strictly controls the pace. The candidate responds as requested. He understands that he must answer questions thoroughly without being long winded, as he expects the interviewer to promptly ask another question.
The structured interview aims to efficiently gain information about the candidate. In this style of interview, the interviewer and candidate typically have just met. The interviewer wishes to gain the same type of information about each candidate so she can evaluate them against each other fairly. When deciding between two or more candidates the firm has previously interviewed, the interviewer may use a semi-structured interview. In this case, she has already gained the most crucial information about the candidates and has weighed their qualifications against each other. She wishes to gain a better sense of the candidates' characters, and a less structured conversation provides this opportunity.
A semi-structured interview's more relaxed nature can help candidates to unwittingly reveal more about themselves. The interviewer may choose this style to encourage candidates to let down their guards. However, interviewers may also ask well-crafted questions in a structured interview to catch a candidate off-guard, in an attempt to learn more than the candidate wishes to reveal. The success of either strategy may depend on the personality of the candidate as well as the skill of the interviewer.
Both structured and semi-structured interviews can incorporate the same types of questions. For instance, they may ask tradition interview questions such as having the candidate detail her strengths and weaknesses. Behavioral questions probe deeper, asking for detailed answers about how the candidate handled particular situations in past jobs. Likewise, both structured and unstructured interviews can take place one-on-one or in a group setting.