Title: Verbal probe interviews
Course: UGQuants (SSPS) > Section: Survey Design

Verbal probe interviews

In the verbal probing method, the interviewer asks the question, the respondent answers following which the interviewer asks for other specific information relevant to the question or answer given. This has become the favoured method for researchers. There are a number of basic types of verbal probes which we will now consider.

Comprehension or interpretation | Probes question respondents’ understanding of particular terms used in the question
Confidence judgement probes | Check how sure a respondent is about details of an answer they have given
Recall probes | Seek to establish how a respondent has arrived at an answer which has required them to retrieve earlier information, for example, ‘how do you remember that you visited the gym seven times in the last month?’
Specific probes | Question respondents as to why they provided a particular response. For example, if respondents were questioned as to what they think the top priority for government funding should be and they chose education, they would be questioned as to the reasons for this choice.
Paraphrasing | The use of paraphrasing as a probe checks respondents’ understanding of questions by asking respondents to put the questions into their own words.
Probes | Can be general in nature for example, asking how the respondent arrived at their answer or how easy / difficult they found the question.

Verbal probes can be either concurrent or retrospective. With concurrent probes, the interviewer asks questions throughout the course of the interview, whereas with retrospective probing, the respondent is asked the probes on completion of the entire survey questionnaire in a debriefing session. The use of concurrent probes is more common. Whilst retrospective probing may be less artificial in allowing the respondent to complete the survey in the usual manner without interruption, valuable information may be lost in waiting until the end of the questionnaire to ask probes as respondents may not remember exactly what they were thinking when answering each question and may simply make up an explanation.

Finally, regardless of the type or category of verbal probe, probes can be either scripted or unscripted. Scripted probes are developed prior to interviewing and are used by all interviewers. Spontaneous probes, however, arise during the course of an interview and are therefore used by particular interviewers only.

The use of verbal probes has a number of advantages. Firstly, the interviewer maintains control of the process, thereby avoiding off topic discussions. Additionally, the interviewer can focus on specific areas that are deemed potential sources of response error. Secondly, unlike think-aloud techniques, respondents can take part in verbal probing interviews with relative ease without the requirement for extensive training.

However, as with the think-aloud method, the use of verbal probes is not without its disadvantages. Firstly, the use of verbal probes throughout an interview is of course not reflective of a usual survey interview, and this artificiality may potentially influence respondents. However, it is important to note that this drawback applies equally to think-aloud techniques. Secondly, the use of verbal probes may carry with it a potential for bias if the probes are conceived as directing respondents to particular answers. It is therefore important that interviewers use non-leading probes.