Students who demonstrate understanding can: Develop a model to generate data for iterative testing and modification of a proposed object, tool, or process such that an optimal design can be achieved.
Official wording from the Next Generation Science Standards (NGSS Lead States, 2013). NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the NGSS were involved in the production of this page, and they do not endorse it. View on nextgenscience.org
Testing a full-size bridge to destruction would be absurd, so engineers test models instead. Students develop a model of a proposed object, tool or process, whether a scale prototype, a computer simulation or a mathematical model, and use it to produce data that guides repeated rounds of change and retesting until the design reaches its best achievable performance.
Each round of this cycle follows the same pattern: test the model, measure the results against the criteria, change one feature, and test again. Changing only one variable at a time shows which modification caused the improvement. Over several iterations, results level off as the design approaches an optimum, the best balance of criteria within the constraints. Students also need to recognize the limits of a model: a cardboard prototype may behave differently from the real product made of steel.
This standard rewards patient, data-driven improvement rather than getting it right the first time.
Real design improves through many test and revise cycles. Early failures provide the data that lead to a better design.
Changing several features together hides which change made the difference, so the next step becomes a guess.
Models simplify reality; size, materials and conditions can make the real object behave differently.
An optimal design is the best balance of the criteria within the constraints, not a flawless one.
A team wants a paper helicopter that falls as slowly as possible from 2 meters. They test blade lengths of 6, 8, 10 and 12 cm, timing 3 drops each. Mean fall times: 1.4 s, 1.8 s, 2.1 s and 2.0 s. What should they conclude and do next?
Answer: About 10 cm blades gave the slowest fall (2.1 s); the team should test lengths close to 10 cm and then tune one other feature at a time.
Paper helicopters, balloon cars and simple simulations are ideal because tests are quick, allowing several iterations in one lesson. Have students keep a design log that records each change, the data, and the reason for the next change. A class graph of performance against iteration number makes the leveling-off toward an optimum visible.
Assessment items often show data from several iterations and ask which change to make next or whether the design has reached an optimum.
Original questions written for this standard. Choose an option or type your answer, then press Check. Every question has a worked explanation.
Answer: D) So you know which change caused the result
Changing one variable at a time links each result to a specific change.
Answer: A) It is cheaper and quicker to test and modify
Models let engineers test many ideas quickly and cheaply before building the real thing.
Answer: B) The design is approaching an optimum
Leveling-off results indicate the design is close to its best possible performance.
Answer: iteration (also accepted: iterative design, iterative testing, iterating)
Iteration means repeated test and improve cycles.
Answer: D) Cardboard may not behave like steel under load
Different materials respond differently, so results may not scale directly to the real bridge.
Answer: 6 (also accepted: 6 N, 6 newtons)
36 - 30 = 6 newtons.
Use a computer simulation to model the impact of proposed solutions to a complex real-world problem with numerous criteria and constraints on interactions within and between systems relevant to the problem.
Design a solution to a complex real-world problem by breaking it down into smaller, more manageable problems that can be solved through engineering.
A full lesson with slides, activities and an exit ticket on models for iterative design testing, pitched to grades 6-8 and editable in PowerPoint or Google Slides.
Make a lesson βA printable, differentiated worksheet on MS-ETS1-4 with an answer key, ready in about a minute.
Make a worksheet βTurn models for iterative design testing into a quiz students answer online that marks itself, with a class summary for you.
Build a test βPhysical prototypes, computer simulations and mathematical models, as long as they generate data for testing and improving the design.
The best achievable balance of the criteria within the constraints, reached through repeated testing and modification.