What are the benefits of an oral exam?
Pedagogical advantages:
- It is much easier to catch misunderstandings early and thus "rescue" an answer. After all, bad exam questions aren't that rare (bad as in: if the student has a very good understanding of the subject, they may be able to guess what topic the examiner has in mind).
- Misconceptions can be corrected: while a written exam gives a snapshot of what the student understood or not, in an oral exam the examiner can ask the student to think again if the answer is wrong. Or can give a counterexample that takes into account the student's answer
- In the end, an oral exam can be a discourse on a subject, which IMHO allows for better/easier grading.
- Related: the difficulty can be adjusted during the exam according to how much the student knows.
- Many oral exams I had had a "mixed" approach for deciding how deep into each subject to go: often 2 subjects were covered in depth (one by choice of the student, one by choice of the examiner) and a number of other topics touched. Particularly letting the student choose a subject of their liking (usually as the beginning of the exam) is not possible with written exams.
Practical consideration:
- if only few students are to be examined, oral exams take much less time for the examiner.
Disadvantage:
- If the examiner is somewhat off in estimating the difficulty of their questions, a written exam at least has the same questions for every student.
Oral and written exams test largely different skill sets. Of course there is some overlap, but not that much. Some examples:
In oral exams you can test the ability to explain things much easier than in a written exam. On the other hand, actual problem solving can be tested easier (and more efficient) in a written exams. In an oral exam you can watch the students thinking (given that you asked the right question), and this gives you the possibility to ask very difficult questions or even question where no answer is known - of course in these cases you should not grade on the base of the "correctness" of the answer, but on the grounds of they approaches the student took. So you can somehow examine if the student did mastered the material to the point that it can be applied to new and unknown situations without the risk of "taking the wrong approach, ran out of time, no points" since you, as examiner, can give feedback on the taken approach but also you can see if the techniques are applied in correctly (even if they will not work out in the end).
A specific example of the latter: If you teach integration techniques and ask the student to find an antiderivative of a complicated function, the student chooses some technique (substitution, say). The technique is applied correctly, but then the student realizes that the substitution was not a good one. By contrast, it could also be, that the student know the right substitution, can explain why this has to work, but fails to work out the details. Both situations may also occur in a written exams, but the examiner can usually not infer what has happened.
Another pedagogic advantage is, that there is immediate feedback for the student, not only during the exam, but also at the end. For a written exam student have to wait somewhere between hours and week to get a grade or even pass-or-fail, while for an oral exam the result is announced after a few minutes (at least where I am).
From the examiners point of view, written exams scale better to large groups, as the grading can be parallelized (by hiring people to do it) or also automated to some extend, while oral exams just scale linearly in the number of students but have a smaller "baseline" (meaning that preparing zero oral exams costs basically zero time while preparing a written exam where nobody shows up, costs a few hours). For me, the break even point is about 25 to 35 students (depending on the topic).
I wrote an answer based on my personal experiences, but here is another based entirely on the literature.
From [1], well-designed oral exams can increase student success:
Scores on the oral examinations in advanced inorganic chemistry are usually about 15–20% higher compared to scores on written examinations over similar material. All students who performed at an unsatisfactory level on the first quiz in the introductory course earned a satisfactory mark after taking the oral quiz. Four probable reasons explain the higher scores:
The most significant contributor to higher grades is the self-correcting nature of the oral format—students always arrive at a correct response before moving on to the next question. This correct response, even though they might have been assisted to reach it, sets the stage for them to answer subsequent questions correctly. On traditional written examinations, missing the first part of a multipart question often results in answering all parts of the question incorrectly.
Requiring students to think aloud during the oral examination makes them think more carefully. This extra measure of care is often evident as a student will start a response, and then, even before they have completed their initial thought, will see a better way to look at the problem and logically work their way to a correct answer from a new starting point.
The oral examination tests a relatively small body of material and students are able to focus their study efforts. This focus is surely intensified by the knowledge that the testing will be done one-on-one. They do not want to do poorly in such a personal situation.
When testing some concepts, such as crystal packing or molarity, the questions are concrete in that students have objects to manipulate.
and this is especially true of weaker students:
Struggling students, in particular, appear to benefit from the oral examination format. The success of these students seems largely to derive from the increase in motivation as a result of personalized strategy instruction, an important component of the ICML. Personalized strategy instruction leads to improved performance and the satisfaction of doing well increases their desire to continue doing well. Many of these weaker students fear college-level chemistry before entering the course. Doing poorly on the first quiz confirms the view they hold of themselves as learners of scientific material. The personal, early intervention that oral quizzes provide enables them to perform better the rest of the semester.
Also, students think that oral exams do a better job of assessing what they know:
Student comments about the oral examinations obtained in anonymous course evaluations and personal exit interviews at the end of the term have always been consistent and enlightening. Most students believe that the oral examination provided a fair reflection of their knowledge. They were satisfied with their performance and would welcome oral examinations in other classes. Most students reported studying more for the oral examinations. Surprisingly, about half of the students interviewed volunteered that the oral examination provided a better reflection of their knowledge compared to written examinations because on written exams they could write something that was “fairly close” to being correct and get by with it. These students thought that the oral exam format made them demonstrate their understanding of the material.
For further reading, here's a small reference list:
[1] Roecker, L., 2007. Using Oral Examination as a technique to assess student understanding and teaching effectiveness. J. Chem. Educ, 84(10), p.1663.
[2] Luckie, D.B., Rivkin, A.M., Aubry, J.R., Marengo, B.J., Creech, L.R. and Sweeder, R.D., 2013. Verbal Final Exam in Introductory Biology Yields Gains in Student Content Knowledge and Longitudinal Performance. CBE-Life Sciences Education, 12(3), pp.515-529.
[3] Dicks, A.P., Lautens, M., Koroluk, K.J. and Skonieczny, S., 2012. Undergraduate oral examinations in a university organic chemistry curriculum. Journal of Chemical Education, 89(12), pp.1506-1510.
[4] Marino, R., Clarkson, S., Mills, P.A., Sweeney, W.V. and DeMeo, S., 2000. Using poster sessions as an alternative to written examination—the poster exam. J. Chem. Educ, 77(9), p.1158.
[5] Pearce, G. and Lee, G., 2009. Viva voce (oral examination) as an assessment method insights from marketing students. Journal of Marketing Education, 31(2), pp.120-130.
[6] Sayre, E.C., 2014. Oral exams as a tool for teaching and assessment. Teaching Science, 60(2), p.29.