Engineers identify criteria and constraints, using trade-offs to balance competing factors.
When facing complex problems, engineers must balance many technical, economic, environmental, social, cultural, and ethical factors. This usually happens early in the engineering design process. However, it is common for additional criteria and constraints to be identified as questions arise later in the process as potential solutions are developed and tested.
In engineering, criteria are the requirements of a design. Constraints are limits that restrict the design. Like engineers, youth’s solutions should be guided by criteria and constraints. Criteria and constraints are often in tension and youth may need to consider trade-offs to optimize their solution. Discussing and posting the criteria and constraints can enhance youth’s designs. Throughout the design process, these criteria and constraints should be referenced as the metric for success.
Criteria are the requirements of a design. They may be related to the design or use of the project. For example, criteria for a baby gate that keeps young children from going up a staircase might include:
Constraints are limits that restrict the design. For the baby gate example, constraints might include the following:
Criteria and constraints are often in tension. A sturdier gate may weigh more. The cheapest or easiest way to open the gate may not be hands-free. Adhering to safety requirements may limit material choices. As they generate ideas, engineers need to be aware of the many parameters and balance the tradeoffs to optimize a solution that fits as many of the criteria and constraints as possible.
Youth learn about balancing criteria and constraints as they work through the Engineering Design Process. You can support developing this practice by engaging youth in talking about trade-offs between competing factors and encouraging them to make their own decisions.
You can also help them think about how they must make trade-offs in other areas of life and the consequences of these decisions – if you finish your homework before you start watching videos afterschool, your parents are less likely to get upset with you. This is a practice that develops as you talk with young people about the decisions they are making.
Criteria and constraints provide the metrics for successful designs. They are often in tension. As youth develop this engineering practice, they will come to understand that any given solution cannot optimize all the criteria and constraints, and that their role as an engineer is to find the best solution possible within the full context of the problem.
Developed in collaboration with Christine M. Cunningham. These practices are also more fully described in educational research articles (Cunningham, 2018; Cunningham & Kelly, 2017).