by Charles Chiu
I have been teaching Engineering Physics, Physics 303K/L, in a large class setting for some years. Physics 303K/L are large service courses offered by the UT Physics Department. For the Fall and Spring semesters the enrollment is about one thousand students per semester. We use an excellent computerized Homework Service System developed by Professor C. Fred Moore and Dr. Herbert Ward. Among other things, their system distributes and collects homework through the Web and the phone. In addition it provides quick grading and immediate feedback. In this article we are mainly concerned with our further efforts in computer-related initiatives, i.e. the use of the Classtalk system and the Web, in our teaching.
The classtalk system: The Classtalk system is a student-instructor interactive system. Through a set of network boxes, students' calculators are connected to the instructor's computer in front of the lecture hall. Our Classtalk project was started with an AT&T Grant. We conducted the first pilot program in weekly discussion sessions in Spring '96. By the end of '96, as a part of a lecture-hall renovation project, we completed installation of two identical systems in two physics lecture halls in the Painter Building. The size of a classtalk system is measured in terms of the number of ports which the system supports. Each of our systems supports 112 ports which serves a 144-seat lecture hall. So the "seat to port" ratio is 1.3, which is the best ratio among all large active Classtalk systems in use today.
We began a full scale operation with one system in the Fall of '96 in our Engineering Physics class. Following the same tradition as the Homework Service System, once the system was working, we involved other enterprising faculty to join this pioneering effort in using the system. In the following semester, i.e. in the Spring of '97, Professors Roger Bengstson, Mike Downer, Jack Turner and I were using both systems. This Fall of '97, six classes are using them. Seven classes are scheduled to use them in the Spring of '98.
Interactive Quiz (IQ) sessions: Different instructors use the Classtalk system differently. We describe our use of the system below. We use a "teaching-physics-through-inquiry" approach, by interspersing a lecture with "interactive quiz" (IQ) sessions. During an IQ session, similar to the "Peer Instruction" approach pioneered by Professor Eric Mazur of Harvard University and used locally by Professor Mike Downer, we encourage students to interact with neighbors, while each student is formulating his/her independent answer.
Our IQ session differs in detail from that used by Professor Mazur's Peer Instruction approach. In Mazur's approach, the students think for one to two minutes about the question of "ConcepTests", and commit to individual answers; then they spend two to three minutes discussing their answers in groups of three or four. After the discussion period, the instructor explains the answer.
In our teaching, all sections of the same course follow a common syllabus and have common exams. In other words, we are constrained to cover the same materials within the same amount of time as those sections where Classtalk is not used. As a consequence we are operating within a very tight time frame. Our approach differs from Mazur's approach in the following two aspects:
IQ questions: The purpose of IQ sessions is to engage student's attention, and turn the conventional passive note-taking experience into a more active learning experience. Among other things, our goals are:
Among the many questions we have made up, each contains an "extra question", which allows those students who have already completed the regular question to move on to this extra-question, so that none of the class is idling.
At this stage, our collection of IQ questions have highlighted a substantial portion of the course material. These questions typically involve 2-3 logical reasoning steps. They illustrate concepts and nuances covered in this course. Due to our time constraints, only a portion of the collection is used in actual IQ sessions. The remainder is used as supplementary lecture material. The entire collection is posted on the Web and is also filed in the library. After each lesson, students are encouraged to review the corresponding IQ questions, which is a convenient way for students to keep up with the pace of the course.
IQ session records: For these IQ sessions, students enter answers using their calculators which are connected to the Classtalk system. While keeping the students' responses anonymous, the system displays the statistical information, which allows instant feedback to students and the instructor.
On a regular basis, IQ session records are transferred manually from the lectern computer to a UNIX machine, where the data are analyzed and class records are generated and posted on the Web. There are also individual students' performance records, which are password protected. Each record may be viewed by the corresponding student and by the instructor. The student's performance record makes the student more aware of his/her daily class participation. It is useful information to the instructor when counseling students. This information may also be taken into account, in assigning student's final grade for the course.
Our homepage: Our Web pages have been a frequently visited place for many students. Within two months after our homepage (http://www.ph.utexas.edu/~ctalk/303Kf97/chiu.html) was created, there have been over 4000 visits. Besides the posting of the IQ questions and students' daily records and other grading records on the Web, there are two important links, which we will now discuss.
Comment Board and Instructor's Comments: The "comment board" allows students to vent their concerns, to post their questions and comments. We find this is an effective way to keep ourselves accountable. We check the comment board on a regular basis and respond to relevant concerns. Sometime we use the Instructor's Comments page to give more in depth analyses of the issues raised. It is worthwile to summarize here several large-class-teaching related issues discussed over the web. Details of of these issues, pros and cons, will remain on the Comment Board and in the Instructor's Comments untill the end of the present semester.
(1) Multiple choice exams: To ensure consistency in grading a large class, we have been using the multiple choice format for our exams. Questions were raised on the Comment Board whether a test in multiple choice format, where intermediate steps are not looked at, can be a fair test.
We believe a test given in this format can be fair, provided great care is exercised in making up the exam. It instructive to use a court case to illustrate the point. Typically the legal situation is complicated. There are many nuances involved. A lawyer needs to spend much time thinking about how to question witnesses, who are expected to give a "yes" or "no", or a very simple answer. Our point is that if a question is well posed, the multiple choice format could be adequate.
In our exams, typically each problem is broken up into two or more questions. Many questions are "textual" questions. We will use them to illustrate our consideration. These questions often directly test student's ability to
We consider them "bare bone" questions. We expect students to perform. Partial credits are not considered. We advise students to identify the key steps of their calculations. During an exam, those important steps need to be gone over several times. We give students ample time, and provide adequate proctor support to make sure students are clear about the questions asked.
We use the analogy that in this course we are training athletes. A test may be compared to setting up 15-20 hurdles. We grade students not on how close they can jump the hurdles, rather on how many they actually jump over. During this semester, I have heard from a number of students, who said they found our exams were fair. Needless to say we will continue to closely monitor the making of multiple choice exams.
(2) Grading multiple choice exams. There are two common grading schemes to grade multiple choice exams: the zero-base-line scheme, where a negative score is assigned to a wrong choice, and the nonnegative scoring scheme. During the present semester, there were outcries from some of the students. They wanted to abolish the negative scoring scheme used in the homework service. Students complained that this scheme appeared to discourage "educated guesses".
During the heat of this controversy, I managed to formulate a mathematical theorem which shows the equivalence of the two grading schemes. More specifically, it turned out, at least for the case, where the number of multiple choices is kept the same for all questons, that the two schemes give identical scaled scores. The scaled scores are the basis of the letter grade assignment. In other words, when one understands the mathematical basis for the two grading schemes, one concludes that the psychological impact on the educated guess using either scheme is the same.
(3) Toward satisfying individual needs. On the comment board one student wrote that he misses the usual red circles, red marks and comments associated with his exam work. Indeed, since the computerized homework/test system does not check student's intermediate steps, it does not give remarks concerning the student's work.
To compensate for this lack of personal attenion, we do encourage students to see us to discuss their test performance on a one-on-one bases. But in a large class how many students can an instructor help, on one-on-one basis? Here is the point where the Web comes to the rescue.
These are examples of how we have used the Web to handle some of the individual needs of the students. Surely more work is needed in the future.
Summary: In summary, high-tech enable us to explore new ways in teaching which was not possible a decade ago. We talked about the use of the Classtalk system in our class using the IQ questions and IQ sessions. We talked about the use the Web beyond the posting of IQ questions and student's records. The Web can be a useful forum for faciliating communication between students and instructor, so that among other things it keeps instructor more accountable in his/her teaching and better serves the students.
We urge students to take the advantage of the approaches which we have discussed in this article. Among other things,