ChemConf '96: Paper 04 - Hypermedia Prelabs

Development and Delivery of Chemical-Education Hypermedia Using the World-Wide Web

Brian M. Tissue

Paper 04, ChemConf '96

Abstract
and Index

1. Introduction

2. Hypermedia

3. Instrumental
Analysis Prelabs

4. Summary

5. References

Section 3: Instrumental Analysis Prelabs

Description of the Prelabs

This section describes the use of hypermedia prelab exercises in a senior-level Instrumental Analysis course during Fall 1995. The course had an enrollment of 28 students and consisted of three hours of lecture and a three-hour laboratory (there were three lab sections with a maximum of 12 students per section). The students worked in groups of 2 or 3 and the groups cycled through four different lab experiments over a four week period. The rationale for implementing computer-based prelabs is to replace prelab lectures that must be repeated for each group at the beginning of every laboratory period. To ensure sufficient access to the internet, three client computers (33-MHz 486 computers with ethernet cards and WWW-browser software) were reserved for the Instrumental Analysis students from 8am to 5pm Monday through Friday in an anteroom to the laboratory. The prelab assignments were worth 10% of the final grade and were graded only on completion and not on the answers. The students were instructed to do the prelab assignments before they came to lab, although no penalty was given for doing the prelabs late. On-line testing has the same intrinsic inability to proctor as a take-home exam or homework.

A prelab assignment consisted of a web page that contained a link to a descriptive tutorial about the experiment or instrumentation and links to interactive exercises. Examples of the prelabs can be viewed at http://www.chem.vt.edu/chem-ed/4114/4114-prelabs.html. Each prelab instructed the student to read the experimental handout before doing the prelab. A printed experimental handout is still necessary as a reference for the students to use when they are actually in the lab. The interactive exercises for most of the prelabs consisted of three multiple-choice questions. The electrochemistry prelabs included one graphics-based exercise with two multiple-choice questions. The graphics-based question consisted of a clickable-map image of the overall experimental set-up. After reading the text description, students were instructed to identify the different instrument components by clicking on them in the graphics image. Clicking on the requested component brought up an enlarged view of that component and the students proceeded on to the next instrument component. An incorrect selection brought up a message to try again and the students could proceed through the exercise only after clicking on the correct component.

Figures 5 and 6 show screen captures of a multiple-choice question and the corresponding response page, respectively. The same response page was returned to the student for either a correct or incorrect answer and included a short explanation of the correct answer.

Fig. 5. Screen Capture of a Multiple-Choice Question Page

Fig. 6. Screen Capture of the Response Page to the Question in Fig. 5

Each question consisted of a question.html file with the multiple-choice question, as shown in Fig. 5, and a question.cgi file.[20] The question.cgi file contained a Perl script that evaluated the answer selected by the student, returned a response page, as shown in Fig. 6, and logged the date, time, and answer in a student file on the server. When grading only on completion, it was easy to count the number of student files in each prelab directory and determine who had not done the assignment. Manually grading large classes or basing the grade on the student answers or on the date and time becomes prohibitively time-consuming. Interpreted languages such as Perl are used in *.cgi files because it is easy to pass input and output between the http server and the script. However, one of the limitations of Perl is that it supports at most two-dimensional arrays (actually one-dimensional arrays of fields).[21, 22, 23] The options are to use more sophisticated programming languages to read and write from databases, or to develop programs or filters to condense, organize, or evaluate the results in the student file(s). We are developing a second generation of Perl scripts that consists of only one script that generates question and answer pages from data files. The current scripts are available at: http://www.chem.vt.edu/chem-ed/CHP/scripts/index.html

Prelab Evaluation

The usage and efficacy of the hypermedia prelabs were assessed from the number and patterns of accesses by users, and from student evaluations. The prelab exercises independently log student answers to student files and were a reliable record of student usage. 21 students completed all 10 prelabs, 5 students completed 8 or 9 prelabs, and 2 students completed less than 5 prelabs, for a 92.5% completion rate. Of the completed prelab assignments, 37% were completed before the day of the lab (includes midnight to 8 am of a student's lab day), 44% were completed on the day of the lab (between 8 am and the beginning of a student's lab period at 2 pm), and 19% of the prelabs were completed late (after the start of a student's lab period at 2 pm). Overall, 75% of the students completed the prelab assignments before the beginning of their lab session.

Student responses to a teacher-designed feedback form were collected twice during the semester.[24] The first mid-semester survey was given after completion of a series of spectroscopy lab experiments and the second survey was given near the end of the semester after completion of a series of electrochemistry experiments. The students had sufficient access to the internet,[25] and greater than 85% of all student usage from the lab computers occurred between 11am and 4pm. Peak usage rather than average usage determines the network and computer capacity needed for unrestricted access to a server. Half of the prelabs were done from the lab computers and half were done from elsewhere: university library, workplace, or home.

The mid-semester assessment of the spectroscopy prelabs suggested that the multiple-choice-question prelab exercises helped the students to understand underlying concepts, but were not as helpful in preparing them to perform the laboratory experiments. The numbers of students who answered "agree" or "strongly agree" was 8 out of 24 for Statement 1: "Doing the prelab exercises helped prepare me for the upcoming laboratory work," and 17 out of 24 for statement 2: "Doing the prelab exercises helped me to understand the underlying concepts," (see Figure 7). In response to these results, we developed a graphics-based exercise for each of the electrochemistry prelabs. The responses to the same statements for the electrochemistry prelabs are shown in Figure 8. There is a small increase in the number of responses indicating that the prelabs helped the students to do the actual lab work. However the differences in the laboratory experiments make it impossible to attribute the higher response to the clickable-map images alone.

Fig. 7. Spectroscopy Prelabs Survey Results

Fig. 8. Electrochemistry Prelabs Survey Results

Comments about the multiple-choice questions ranged from "too easy" and "could guess the answers" to "enlightening" and "helped me understand underlying concepts." There was one comment from a home user who complained that downloading the graphics was too slow, and another student had difficulty accessing the material from a dormitory computer lab. Two students commented that using the internet was a valuable skill that they learned from doing the prelabs, and only 4 of 23 students would prefer to have the exercises delivered by CD-ROM.[26]