Science teachers face the challenge of teaching science content so that it relates to actual situations. The National Science Education Standards (National Research Council, 1996) provides guidelines for teaching content and connecting it to student experiences. However, in many cases, a disconnect exists between “school science” and “real science.” School science can be defined as science taught to students in schools while real science is science practiced by scientists. In many schools, real science often plays a secondary role to school science so teachers can complete their curriculum. But it doesn’t have to be this way. Educators can use a teaching technique called problem-based learning (PBL) to combine both school and real science.

What is PBL?

PBL is a curricular design that centers on an authentic problem. During a PBL activity, acquiring content knowledge occurs simultaneously with solving the problem. This differs from a typical science teaching approach in which the problem is presented to students after they learn the required content knowledge. In a PBL activity, students are cast in realistic roles and presented with an “ill-structured” problem—a complex situation that has no single, clear-cut solution. Because the problem is unclear and there are multiple solutions to it, questions arise regarding the information and understanding needed to solve the problem. Students control the direction of their own learning as they decide what they need and want to know to construct a solution to the problem.

Problem design

The first step to designing an ill-structured problem is deciding on the problem’s objectives. These objectives should be based on local, state, and national science education standards. Once the objectives for the problem are determined, brainstorming of possible PBL problems can begin.

Howard Barrows (1994), a neuroscientist and one of the founders of PBL, states that a problem must be authentic to maximize student motivation and learning. An easy way to construct a problem is to base it almost entirely on a past or present event. Newspapers and news magazines are good places to find local science issues. For example, a local newspaper reported that the childhood leukemia rate in a neighboring community was twice the national rate. Students could determine why this discrepancy exists. Another issue is the recent mandate by the federal government to lower arsenic concentrations in drinking water to 10 ppb. Students could decide if this law can be reasonably enacted by their local water districts. Other places to find events on which to base problems may include web-based journals such as the Mortality and Morbidity Weekly Report (MMWR) on the website (www.cdc.gov/mmwr/) for the Centers for Disease Control (CDC). This electronic journal discusses disease outbreaks that have been reported to the CDC and lists data used by physicians to diagnose the disease.

Once an event has been found, teachers can craft the science issue into a PBL problem. One of the many different PBL organizing and teaching frameworks can be found at the Center for Problem-Based Learning at the Illinois Math and Science Academy (IMSA) website at www.imsa.edu/team/cpbl/problem.html. The IMSA website has easy-to-use, step-by-step instructions for teachers on how to develop a PBL activity as well as completed PBL problems available for viewing and use. While the PBL teaching framework we use is a combination of IMSA, Barrows (1994), Gallagher (1995), and the Center for Gifted Education at the College of William and Mary (1997), teachers we have worked with have found the IMSA framework the best organized and easiest for novices to understand.

For a class activity to be a PBL problem: 1) the students must be able to picture themselves in a role described in the PBL problem and successfully construct a solution to the problem, and 2) the problem must be “ill-structured” as previously described (Greenwald, 2001; Gallagher, 1995). PBL problems should not be developed as another classroom assignment, such as having a single answer derived from a single method of analysis (Barrows, 1994), rather PBL problems have several parts depending on the model used to construct the problem and the objectives of the problem (Figure 1).

Finding and preparing data

In a PBL problem, data is used to design the problem and give students clues about possible solutions. In some cases—especially with real events—data already exists. Data from actual events can be obtained from various governmental agencies by visiting a library, browsing the Internet, or contacting the agency by phone or e-mail.

The instructor must then put the data into a usable format. The objectives of the PBL problem should be considered in determining the amount of data the instructor should process for students. Because students should spend more time analyzing data for meaning and figuring out how it applies to the problem, data must be cleaned up and streamlined for easier interpretation. This leads to multiple methods of student analysis.

In some cases actual data does not exist; however, information about what the data could be is available, which then allows data set construction. Information about data can be found in professional trade manuals or textbooks, for example, Harrison’s Principles of Internal Medicine (Isselbacher et al, 1994) or the MERCK Manual of Diagnosis and Therapy (www.merck.com/pubs/mmanual). In a medical PBL problem, these references help the instructor construct a data set by providing information that is essential to diagnose the disease.

Determining the format and amount of data to give students is a difficult decision. One way to ascertain if data is in an appropriate format is to field test the data set with a group of students and note the difficulties students encounter. The instructor can assess whether students have trouble understanding and using a particular piece of data or if essential data is missing.

The amount of content students must have before working with a PBL problem is still a matter of controversy. Some PBL practitioners advocate introducing a problem when students have no prior content knowledge, while others support varying amounts of student preparation. How much prior knowledge students should have depends on the content objectives of the PBL problem.

For example, in the water management PBL problem shown in Figure 2, prior knowledge about the complexity of ground and surface water systems helped some students think critically about water demands, influences on water quality, and the behavior of surface water as groundwater is used. However, students with less prior knowledge had more creative ideas for water conservation programs that met the goals of the water management plan.

PBL in the classroom

PBL uses cooperative student groups to work through a problem. After the problem has been presented, students brainstorm to create a list of either facts, hypotheses, and what needs to be learned, or, alternatively, what students know and what students need to know. As they become more adept at brainstorming, the teacher can decrease the amount of scaffolding required to support student work. At this point in the process, some PBL teaching models have students clarify the problem in a single, concise statement to focus student work. After the initial brainstorming session, students gather data and information relevant to the problem. When a student group has reached a point where they cannot proceed without more data specific to the problem, the instructor first questions students to assess depth of knowledge and understanding and then gives the group the needed data.

Assessing student knowledge

Student understanding can be assessed in a number of ways, including giving students the “answer” to the problem. The students evaluate the instructor’s answer based on what they learned from the problem. For example, if students have a diagnosis for a patient, they can judge whether or not the diagnosis is reasonable. Another way to assess students is to have them present their solutions. For instance, students who create a plan to manage the reintroduction of an endangered species can present the plan to a panel of community representatives. Regardless of how learning is determined, the more authentic the student assessment is, the higher the quality of student products. To assist student product assessment, community members, other teachers, and university students and faculty can act as patients, city council members, and governmental agency representatives.

An essential part of PBL is for students to conduct self-reflection and self-assessment on how well individuals worked with each other (Barrows, 1994). This can be done by using both an anonymous questionnaire, which allows students to make constructive comments about themselves and others in the group, and an open discussion in which self-reflection and positive reinforcement are used to develop cooperative group skills and build group dynamics.

Rubrics are used in my classes to assess student understanding and presentation quality. The rubrics are given to students at the beginning of the PBL activity and provide the students detailed information about what will be evaluated during their presentations. Students can use the rubrics as a guide to determine which information should be included in the presentation as well as how the presentation should be structured. A sample content rubric is shown in Figure 3.

Benefits of PBL

Using PBL problems as the center of a science curriculum provides several benefits. Students have control over their own learning and are focused on the problem with a specific goal and timeframe. In addition, because students often learn content as they work with the problem, time is saved because the presentation of basic information is eliminated. Clear statements of performance objectives and constant self-evaluation direct students to information to be learned from the PBL problem.

The main benefit to students is developing an understanding of the connection between science and society. Students see the importance of using concepts from specific science disciplines to explain collected data to influence government policies. Furthermore, students gain knowledge of how science and mathematics are used to make predictive models about future events, to explore the limitations of these models, and to see the need for continued scientific research to improve these models.

Designing a PBL problem and getting the materials ready for student use is time-consuming; the availability of time for the teacher increases as the students begin work on the problem. Because less time is spent directly instructing the whole class, the teacher can spend more time monitoring and assisting individual students. Admittedly, using PBL continuously—as with any pedagogy that has a high cognitive level—is tiring to the students and the instructor. However, prudent use of PBL can not only teach important science concepts at a deep, comprehensive level to all students but also situate science in the world of students’ experiences.

Steve Uyeda (e-mail: suyeda@u.arizona.edu) is a science teacher at Catalina Foothills High School, 4300 East Sunrise Drive, Tucson, AZ 85718; John Madden (e-mail: maddenj1@mindspring.com) is a science teacher at Mountain View High School, 3901 West Linda Vista Boulevard, Tucson, AZ 85742; Lindy A. Brigham (e-mail: lbrigham@ag.arizona.edu) is an assistant research professor at the College of Agriculture, University of Arizona, Tucson, AZ 85721–0036; Julie A. Luft (e-mail: luft@u.arizona.edu) is an associate professor at the College of Education, University of Arizona, Tucson, AZ 85721; and Jim Washburne (e-mail: jwash@hwr.arizona.edu) is an assistant adjunct professor at the College of Engineering and Mines, University of Arizona, Tucson, AZ 85721–0011.

References

Barrows, H.S. 1994. Practice-Based Learning: Problem-Based Learning Applied to Medical Education. Springfield, Ill.: Southern Illinois University School of Medicine.
The College of William and Mary. 1997. Guide to Teaching a Problem-based Science Curriculum. Dubuque. Iowa: Kendall/Hunt Publishing.
Gallagher, S., W.J. Stepien, B.T. Sher, and D. Workman. 1995. Implementing problem-based learning in science classrooms. School Science and Mathematics 95(3): 136–146.
Greenwald, N.L. 2000. Learning from problems. The Science Teacher 67(4): 28–32.
Isselbacher, K.J., Martin, J.B., Braunwald, E., Fauci, A.S., Wilson, J.D., Kaspar, D.L., eds. 1994. Harrison’s Principles of Internal Medicine. New York: McGraw-Hill.
National Research Council. 1996. National Science Education Standards. Washington, D.C.: National Academy Press.

Acknowledgment

This work is supported in part by SAHRA (Sustainability of semi-Arid Hydrology and Riparian Areas) under the STC Program of the National Science Foundation, Agreement EAR-9876800. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of SAHRA or of the National Science Foundation.