Prior to implementing a design, engineers make decisions based on evidence that a given design will work; they rarely rely on trial and error. The evidence is often based on an analysis that predicts performance for a given configuration of variables. In several curricular projects, students are required to manipulate and test variables in various configurations to discover the patterns that can inform or optimize a design. This form of analysis is found in “A World in Motion,” “City Technology,” “Engineering is Elementary,” and “Material World Modules.” One of the richest treatments of this kind of analysis was in the Glider unit in “A World in Motion.”
In contrast to engineering practice, the curricula provide few opportunities for analysis of the economic feasibility of a given design or of the relative feasibility of competing designs. However, economic factors that can influence design are addressed in “Building Math,” “Design and Discovery,” and “Engineering the Future.” For example, in “Building Math,” middle school students perform a variety of mathematical computations to design optimal interventions to contain the spread of a virus in a village in the Amazon rain forest on a budget of $10,000. In the “Design and Discovery” curriculum, students compare the costs and trade-offs associated with using different materials for beverage containers (e.g., aluminum, glass, plastic). In an exercise in “Engineering the Future” students perform simple calculations to estimate the cost of materials and production, project a retail price, and estimate the competitiveness of a product in the marketplace.
Many curricular materials encourage students to evaluate alternative design options. These analyses typically involve unstructured discussion among students working in a group about the perceived merits of each option to arrive at a consensus about which option should be further developed. For example, in “Building Math,” middle school students design an insulated container of medicine that will maintain a temperature of 59°F to 86°F for a minimum of two hours. After gathering data about the insulating properties of various materials, each member of the design team sketches an idea for a container, describes it to the other members of his or her team, and then, “as a group,” they “decide on one ‘best’ solution.” None of the curricula include procedures or expectations for conducting a formal analysis of alternative solutions, such as a trade-off matrix for making quantitative comparisons of the strengths and weaknesses of competing designs (Garmire, 2002).
Investigating failure as a specific line of analysis appears in only a few curriculum projects. A good example, from the Packaging and Other Structures unit in the “City Technology” curriculum, requires elementary students to fill paper and plastic bags with containers of water until they fail. The