The case study method of instruction offers a less didactical approach to instruction in the natural sciences. The case method stresses the development of students' communication and higher order thinking skills; it encourages them to engage in critical analysis and involves active student participation as its hallmark.
Despite these strengths, the case study method was seldom used in undergraduate instruction in the sciences. Recently, however, its use for undergraduate instruction in the natural sciences has been effectively championed by Clyde F. Herreid, and it is currently growing (Herreid, 1994). The case study method, however, has a significant limitation. It is not effective for the transmission of large amounts of factual information. This limits its use as the primary mode of instruction in information-intensive science courses.
In 1993 the authors became aware of an active learning instructional method, Team Learning, that was developed to teach organizational behavior classes at the University of Oklahoma (Michaelsen, 1992). We believed that, extensively modified, Team Learning could be used for instruction in introductory science courses, and could overcome many of the lecture method's weaknesses while retaining its strengths. In 1993 a modified team learning method which we now term Problem Based Team Learning (PBTL) was introduced at Canisius College (Dinan, 1995) where it is now used for instruction in a variety of information-intensive science and mathematics courses.
Whereas PBTL eliminates some of the flaws of the lecture method, it too has its limitations. PBTL is not as effective as the case study method for teaching higher order thinking skills and fostering students' ability to make critical judgments. We have, therefore, combined PBTL and case study teaching for use in many of our courses. Our experience with the use of the case study method in these courses is presented here.
Our introductory level science courses meet four times per week. Three of these meetings are fifty-minute "lecture" classes that are used to present new information using the PBTL method. The fourth class each week is a seventy five-minute "recitation" class. It is here that our case study teaching takes place.
Avogadro's number and the mole concept are initially taught in the PBTL portion of our general chemistry course. The purpose of our Avogadro's number case study is to make these abstract concepts more interesting and concrete for our students.
This case study was inspired by a newspaper report of a professor who was sued by his students over an assignment that he had given them dealing with Avogadro's number (Anonymous, 1995). The report explained that the professor had asked his students to calculate the cost of a single aluminum atom contained in a roll of aluminum foil--a problem that required them to properly use Avogadro's number and the mole concept. The students had a great deal of trouble doing this calculation. They claimed they got little help from their professor, whom they eventually sued. The judge that tried the case ruled in the students' favor.
Our Avogadro's number case study presents our students with this newspaper account and asks them to use Avogadro's number and the mole concept to do the calculation that was asked of the other students. This requires them to think through the exact information they need in order to do this calculation, how it can be obtained, and how Avogadro's number and the mole concept must be used to obtain the answer. The materials the students are given contain a plea to "please keep your instructor out of jail."
Another example of a single subject case study is our Gasoline Cost Case. This case study is used to address a problem common to many beginning science students: learning the proper use of dimensional analysis to document the inter-conversion of varied units of measurement.
Whereas learning the proper use of dimensional analysis can be challenging for beginning science students, the relative costs of American and Canadian gasoline is always interesting to our budget conscious students in this Canadian/American border region. Since the two nations use different volume measurement units and currencies, this cost comparison requires that a number of unit inter-conversions be carried out.
An article in a local Canadian newspaper claimed that the cost of gasoline in the Buffalo, New York, area offered no advantage over the cost of Canadian gasoline. This afforded us an opportunity to write a case study that would apply dimensional analysis in a concrete and interesting way. The case study focused on the newspaper article's claim and asked our students to check its validity. The students were asked to calculate the relative costs of American and Canadian gasoline, and to document their calculations by writing a detailed dimensional analysis of their method. They were relieved to find that Canadian gasoline was more expensive than American gasoline. We then asked the student teams to determine the circumstances under which a Canadian driver would benefit economically from crossing the border to purchase gasoline, and to list all of the assumptions they had to make (driving distance, tank size, bridge tolls, etc.) to answer this question accurately. This case requires a higher degree of critical thinking and analysis than is characteristic of many introductory level science problems; the student teams approached it enthusiastically.
It is important to note that both of these cases are taught within the first week of the freshman course in which they are used. At this critical time in the evolution of this course, and in our students' college careers, thess cases serve both a teaching and a highly important socialization purpose. The real-world nature of these case studies and the use of student teams to teach them helps to overcome initial student reticence, foster the development of good communication skills, and promote positive social interactions within the teams.
Students today routinely use the Internet as an information source. They tend to search the Internet in preference to more conventional literature sources despite the fact that Internet information tends to be voluminous, diffuse, unedited, and of highly uneven credibility. Recognizing this, we allowed the student teams to use both Internet and standard information sources for this case hoping that they would clearly see the qualitative differences that characterize the two.
The methamphetamine synthesis case study was inspired by a media report of an explosion that injured some neophyte chemists who were involved in the illicit synthesis of the hallucinogenic drug, methamphetamine. The report gave no information about the cause of the explosion, or the chemicals being used by its victims. The student teams were asked to find ways to prepare methamphetamine, and to decide how an explosion might occur during its preparation.
Each team conducted its own information search and reported on the details of the procedures they found for the preparation of methamphetamine. The teams were then assigned to evaluate the merits of the various methamphetamine preparation methods, and to rank them in terms of their relative quality.
Students in organic chemistry quickly become aware that many potential synthetic routes of varying quality exist for the synthesis of organic molecules. Assessing the relative merits of these routes is a challenging undertaking for beginning students. Because this case stimulated their interest, the teams worked hard at finding ways to prepare methamphetamine and on evaluating their relative quality.
An additional resolution of conflict case study that we have developed asks our students to compare the merits of conventional ethylene glycol (EG)-based antifreeze mixtures to those of a newly marketed propylene glycol (PG)-based antifreeze mixture. An important observation in this case study is that EG and PG differ greatly in their taste. Antifreeze mixtures based upon EG reportedly have a sweet taste that is attractive to animals, and EG is known to be quite toxic when ingested (Budavari, 1990). Concerns about the environmental safety of EG-based antifreeze surfaced after media reports attributed the deaths of deer and dogs to the consumption of improperly disposed EG-based antifreeze.
The new PG-based antifreeze mixtures apparently came into being in response to the concerns raised by these reports. In contrast to EG, PG is reported to have a bitter taste. Pure PG is also significantly less toxic than is pure EG (Budavari, 1990). The new PG-based antifreeze mixture is advertised as being environmentally friendly and sells for a seventy five percent premium over the cost of conventional antifreeze mixtures.
Our students were given a summary of this information and were asked to evaluate the two types of antifreeze mixtures with respect a variety of their characteristics. Among these are their relative toxicity, their methods of manufacture, the nature and toxicity of the corrosion inhibitors that must be added to them, and what, if anything, could be done to change the attractiveness of EG to animals.
Each of these research questions was assigned to one person on each team. These individuals then researched their assigned topics. Upon reassembling, information was shared using the "jigsaw" technique. This method first brings the students specializing in a given question together in a group where they share their information. After this, the question specialists return to their permanent teams to share the information they have gathered with their team members. The teams then use the information available to them to formulate answers to the assigned questions. After orally reporting their conclusions to the class, each team writes a short report that explains how they came to their conclusions, and lists their supporting data and references.
Stereochemistry, the study of the three-dimensional arrangement of atoms in space, is typical of many concepts that beginning students find to be complex and highly abstract. A molecule must have the correct three-dimensional spatial arrangement of atoms if it is to function properly in living things. Simply stating this fact, however, makes little impression on many beginning students who fail to grasp this idea.
An Internet site found by our students during their searches for ways to prepare methamphetamine claimed that the drug could readily be extracted from an easily available non-prescription pharmaceutical. We asked the student teams to assess the validity of this claim. Upon doing so, they concluded that the three-dimensional form of methamphetamine that would be obtained from this procedure would not have the stereochemical arrangement required for it to be biologically active. This realization provided an interesting and practical insight into the real-world value of an otherwise abstract topic and demonstrated the potential unreliability of Internet-derived information.
After their initial research is complete, each team makes an oral presentation to the instructor in which they describe the method they propose to use. At this conference, a general experimental procedure is agreed upon. The students then detail the procedure in writing and present it to their instructor. If this procedure is found to be safe and satisfactory, the students are authorized to begin their experimental work. Two examples of case studies that have been used in this course are described briefly below. The student teams are required to complete three case studies of this type during the second half of this course.
The Nut Case describes a situation in which a supplier allegedly attempted to substitute a cheaper type of groundnut, walnuts, for a more expensive variety of groundnut, pecans. Surprisingly, it is difficult to distinguish between the taste of these nuts without accompanying visual clues, and the finely groundnuts cannot be readily distinguished. The students are asked to construct an analytical method that would clearly distinguish pecans from walnuts and would allow them to decide the fate of the allegedly unethical supplier.
The Hot or Cold Case states that a knowledgeable chemist asserted that if tea were brewed in the refrigerator, only the flavor components would be extracted into the cold water, not the caffeine. This, the case study alleges, is because the solubility of caffeine in water is slight at low temperatures and increases at the higher temperatures used when tea is brewed in boiling water. In contrast, the flavor components of tea are alleged to be water soluble even at low temperatures. The students are asked to develop a procedure that will allow them to experimentally confirm or refute the chemist's assertion.
A wide variety of case studies chosen to be socially controversial and to involve complex science-based technological arguments have been written for use in this course. Some of these focus on global warming, pesticides in foods, breast implant safety, and other topics of similar importance. These major issue cases are well suited for study using the techniques of risk/benefit analysis, a method widely used to resolve difficult social/technological questions. The student teams are asked to analyze their assigned positions for each case study using risk/benefit analysis (Slovic, 1979) as their primary decision making method.
These case studies require that important issues that underlie these social/technological controversies but are seldom dealt with in mainstream science courses be considered. Among these are the characteristics of risk perception, statistical versus other types of evidence, and the roles played by the legal profession, government regulatory groups, expert witnesses, and public interest groups in determining the outcome of these controversies.
Procedurally, the teams are presented with the case study and receive their assigned position. The data-gathering phase then begins. Next, each team writes a brief report outlining the arguments and listing the literature references that support their assigned position. After the teams have presented their arguments to the class orally, they are charged with trying to resolve the conflicts that characterize their positions. This is an exercise in risk/benefit analysis that requires the use of higher order thinking skills, and careful critical analysis.
The case studies approach is superior to the classical approach for laboratory instruction in science. The case approach we have described allows students to deal with problems that more closely approximate those that they will encounter as practicing professionals. It is more interesting and exciting for students since it requires them to think about their work at a higher level by virtually eliminating the "cookbook" approach to laboratory instruction.
Placing students in small teams when teaching case studies allows us to present them with more complex problems than we would consider assigning to individual students. Our students report that this increased ability to deal with complexity results from two not unrelated factors: an increase in confidence, and a reduction of anxiety. The anxiety factor is not trivial. Anxiety that stems from being confronted with a challenging problem can have a paralyzing effect on students who are entirely capable of dealing with the problem if they can get started. The team provides these students with a blend of peer support and peer pressure that raises their confidence levels and, ultimately, their performance.
A completely unanticipated benefit resulting from our use of case studies in laboratory courses is that work is nearly universally completed on time. The combination of the interest generated by the case studies together with the peer support and pressure that results from the group structure combine to routinely accomplish what threats, pleas, and abject pleading have often failed to accomplish in the past. Procrastination has been greatly diminished, if not completely vanquished.
Additionally, we routinely see our students exhibiting a higher level of thinking and critical analysis skills than they have exhibited in the past. This change, our studies indicate, is the result of our shift from classical methods of instruction to the combined PBT/case studies approach described here. Finally, and perhaps most importantly, our data indicate that the overwhelming majority of our students both enjoy and feel that they benefit from this approach to teaching/learning.
