The case study teaching method is a highly adaptable style of teaching that involves problem-based learning and promotes the development of analytical skills (8
). By presenting content in the format of a narrative accompanied by questions and activities that promote group discussion and solving of complex problems, case studies facilitate development of the higher levels of Bloom’s taxonomy of cognitive learning; moving beyond recall of knowledge to analysis, evaluation, and application (1
). Similarly, case studies facilitate interdisciplinary learning and can be used to highlight connections between specific academic topics and real-world societal issues and applications (3
). This has been reported to increase student motivation to participate in class activities, which promotes learning and increases performance on assessments (7
). For these reasons, case-based teaching has been widely used in business and medical education for many years (4
). Although case studies were considered a novel method of science education just 20 years ago, the case study teaching method has gained popularity in recent years among an array of scientific disciplines such as biology, chemistry, nursing, and psychology (5
Although there is now a substantive and growing body of literature describing how to develop and use case studies in science teaching, current research on the effectiveness of case study teaching at meeting specific learning objectives is of limited scope and depth. Studies have shown that working in groups during completion of case studies significantly improves student perceptions of learning and may increase performance on assessment questions, and that the use of clickers can increase student engagement in case study activities, particularly among non-science majors, women, and freshmen (7
). Case study teaching has been shown to improve exam performance in an anatomy and physiology course, increasing the mean score across all exams given in a two-semester sequence from 66% to 73% (5
). Use of case studies was also shown to improve students’ ability to synthesize complex analytical questions about the real-world issues associated with a scientific topic (6
). In a high school chemistry course, it was demonstrated that the case study teaching method produces significant increases in self-reported control of learning, task value, and self-efficacy for learning and performance (24
). This effect on student motivation is important because enhanced motivation for learning activities has been shown to promote student engagement and academic performance (19
). Additionally, faculty from a number of institutions have reported that using case studies promotes critical thinking, learning, and participation among students, especially in terms of the ability to view an issue from multiple perspectives and to grasp the practical application of core course concepts (23
Despite what is known about the effectiveness of case studies in science education, questions remain about the functionality of the case study teaching method at promoting specific learning objectives that are important to many undergraduate biology courses. A recent survey of teachers who use case studies found that the topics most often covered in general biology courses included genetics and heredity, cell structure, cells and energy, chemistry of life, and cell cycle and cancer, suggesting that these topics should be of particular interest in studies that examine the effectiveness of the case study teaching method (8
). However, the existing body of literature lacks direct evidence that the case study method is an effective tool for teaching about this collection of important topics in biology courses. Further, the extent to which case study teaching promotes development of science communication skills and the ability to understand the connections between biological concepts and everyday life has not been examined, yet these are core learning objectives shared by a variety of science courses. Although many instructors have produced case studies for use in their own classrooms, the production of novel case studies is time-consuming and requires skills that not all instructors have perfected. It is therefore important to determine whether case studies published by instructors who are unaffiliated with a particular course can be used effectively and obviate the need for each instructor to develop new case studies for their own courses. The results reported herein indicate that teaching with case studies results in significantly higher performance on examination questions about chemical bonds, osmosis and diffusion, mitosis and meiosis, and DNA structure and replication than that achieved by class discussions and textbook reading for topics of similar complexity. Case studies also increased overall student perceptions of learning gains and perceptions of learning gains specifically related to written and oral communication skills and the ability to grasp connections between scientific topics and their real-world applications. The effectiveness of the case study teaching method at increasing academic performance was not correlated to whether the case study used was authored by the instructor of the course or by an unaffiliated instructor. These findings support increased use of published case studies in the teaching of a variety of biological concepts and learning objectives.
The purpose of this study was to test the hypothesis that teaching with case studies produced by the instructor of a course is more effective at promoting learning gains than using case studies produced by unaffiliated instructors. This study also tested the hypothesis that the case study teaching method is more effective than class discussions and textbook reading at promoting learning gains associated with four of the most commonly taught topics in undergraduate general biology courses: chemical bonds, osmosis and diffusion, mitosis and meiosis, and DNA structure and replication. In addition to assessing content-based learning gains, development of written and oral communication skills and the ability to connect scientific topics with real-world applications was also assessed, because these skills were overarching learning objectives of this course, and classroom activities related to both case studies and control lessons were designed to provide opportunities for students to develop these skills. Finally, data were analyzed to determine whether performance on examination questions is positively correlated to student perceptions of learning gains resulting from case study teaching.
Compared with equivalent control questions about topics of similar complexity taught using class discussions and textbook readings, all four case studies produced statistically significant increases in the mean score on examination questions (Fig. 1
). This indicates that case studies are more effective than more commonly used, traditional methods of content delivery at promoting learning of a variety of core concepts covered in general biology courses. The average increase in score on each test item was equivalent to nearly two letter grades, which is substantial enough to elevate the average student performance on test items from the unsatisfactory/failing range to the satisfactory/passing range. The finding that there was no statistical difference between case studies in terms of performance on examination questions suggests that case studies are equally effective at promoting learning of disparate topics in biology. The observations that students did not perform significantly less well on the first case study presented (chemical bonds) compared with the other case studies and that performance on examination questions did not progressively increase with each successive case study suggests that the effectiveness of case studies is not directly related to the amount of experience students have using case studies. Furthermore, anecdotal evidence from previous semesters of this course suggests that, of the four topics addressed by cases in this study, DNA structure and function and osmosis and diffusion are the first and second most difficult for students to grasp. The lack of a statistical difference between case studies therefore suggests that the effectiveness of a case study at promoting learning gains is not directly proportional to the difficulty of the concept covered. However, the finding that use of the osmosis and diffusion case study resulted in the greatest increase in examination performance compared with control questions and also produced the highest student perceptions of learning gains is noteworthy and could be attributed to the fact that it was the only case study evaluated that included a hands-on experiment. Because the inclusion of a hands-on kinetic activity may synergistically enhance student engagement and learning and result in an even greater increase in learning gains than case studies that lack this type of activity, it is recommended that case studies that incorporate this type of activity be preferentially utilized.
Student perceptions of learning gains are strongly motivating factors for engagement in the classroom and academic performance, so it is important to assess the effect of any teaching method in this context (19
). A modified version of the SALG course evaluation tool was used to assess student perceptions of learning gains because it has been previously validated as an efficacious tool (Appendix 2
). Using the SALG tool, case study teaching was demonstrated to significantly increase student perceptions of overall learning gains compared with class discussions and textbook reading (Fig. 2A
). Case studies were shown to be particularly useful for promoting perceived development of written and oral communication skills and for demonstrating connections between scientific topics and real-world issues and applications (Figs. 2B–2D
). Further, student perceptions of “great” learning gains positively correlated with increased performance on examination questions, indicating that assessment of learning gains using the SALG tool is both valid and useful in this course setting (Fig. 3
). These findings also suggest that case study teaching could be used to increase student motivation and engagement in classroom activities and thus promote learning and performance on assessments. The finding that textbook reading yielded the lowest student perceptions of learning gains was not unexpected, since reading facilitates passive learning while the class discussions and case studies were both designed to promote active learning.
Importantly, there was no statistical difference in student performance on examinations attributed to the two case studies produced by the instructor of the course compared with the two case studies produced by unaffiliated instructors. The average difference between the two instructor-produced case studies and the two case studies published by unaffiliated instructors was only 3% in terms of both the average score on examination questions (76% compared with 73%) and the average increase in score compared with paired control items (14% compared with 17%) (Fig. 1
). Even when considering the inherent qualitative differences of course grades, these differences are negligible. Similarly, the effectiveness of case studies at promoting learning gains was not significantly affected by the origin of the case study, as evidenced by similar percentages of students reporting “good” and “great” learning gains regardless of whether the case study was produced by the course instructor or an unaffiliated instructor (Table 1
The observation that case studies published by unaffiliated instructors are just as effective as those produced by the instructor of a course suggests that instructors can reasonably rely on the use of pre-published case studies relevant to their class rather than investing the considerable time and effort required to produce a novel case study. Case studies covering a wide range of topics in the sciences are available from a number of sources, and many of them are free access. The National Center for Case Study Teaching in Science (NCCSTS) database (http://sciencecases.lib.buffalo.edu/cs/
) contains over 500 case studies that are freely available to instructors, and are accompanied by teaching notes that provide logistical advice and additional resources for implementing the case study, as well as a set of assessment questions with a password-protected answer key. Case study repositories are also maintained by BioQUEST Curriculum Consortium (http://www.bioquest.org/icbl/cases.php
) and the Science Case Network (http://sciencecasenet.org
); both are available for use by instructors from outside institutions.
It should be noted that all case studies used in this study were rigorously peer-reviewed and accepted for publication by the NCCSTS prior to the completion of this study (2
); the conclusions of this study may not apply to case studies that were not developed in accordance with similar standards. Because case study teaching involves skills such as creative writing and management of dynamic group discussion in a way that is not commonly integrated into many other teaching methods, it is recommended that novice case study teachers seek training or guidance before writing their first case study or implementing the method. The lack of a difference observed in the use of case studies from different sources should be interpreted with some degree of caution since only two sources were represented in this study, and each by only two cases. Furthermore, in an educational setting, quantitative differences in test scores might produce meaningful qualitative differences in course grades even in the absence of a p
value that is statistically significant. For example, there is a meaningful qualitative difference between test scores that result in an average grade of C− and test scores that result in an average grade of C+, even if there is no statistically significant difference between the two sets of scores.
In the future, it could be informative to confirm these findings using a larger cohort, by repeating the study at different institutions with different instructors, by evaluating different case studies, and by directly comparing the effectiveness of the case studying teaching method with additional forms of instruction, such as traditional chalkboard and slide-based lecturing, and laboratory-based activities. It may also be informative to examine whether demographic factors such as student age and gender modulate the effectiveness of the case study teaching method, and whether case studies work equally well for non-science majors taking a science course compared with those majoring in the subject. Since the topical material used in this study is often included in other classes in both high school and undergraduate education, such as cell biology, genetics, and chemistry, the conclusions of this study are directly applicable to a broad range of courses. Presently, it is recommended that the use of case studies in teaching undergraduate general biology and other science courses be expanded, especially for the teaching of capacious issues with real-world applications and in classes where development of written and oral communication skills are key objectives. The use of case studies that involve hands-on activities should be emphasized to maximize the benefit of this teaching method. Importantly, instructors can be confident in the use of pre-published case studies to promote learning, as there is no indication that the effectiveness of the case study teaching method is reliant on the production of novel, customized case studies for each course.