Conducting a Fair Test in Engineering Design – What You Need to Know

Conducting a fair test in engineering design? This phase of the process is often overlooked. But kids in third, fourth, and fifth grades should do it! After identifying failure points, they select one variable to manipulate. Read more to implement this in your classroom.

Ms. Sneed Explains Conducting a Fair Test in Engineering Design

Once again, our favorite fourth grade teacher sat at the side table with her student teacher. “Today,” she said, “we’ll work on a really important – but frequently overlooked – part of the engineering design process. Conducting a fair test is a critical part of the strategies we use for redesigning a prototype.”

“It sounds familiar,” Mr. Grow replied.

“Yes, you’ve probably heard the term used as part of the scientific method. You know, the part where we control only one variable.”

Mr. Grow nodded. As he opened his plan book, he reviewed the lessons they’d already discussed. “First, talked about defining a problem with criteria and constraints. Second, we planned activities for generating and choosing solutions. Third, developing and testing a prototype.”

“And don’t forget – when they tested the prototype, they also identified failure points. That’s where we pick up our conversation.”

Introducing the Fair Test with a Story

“As before,” Ms Sneed continued, “we’ll introduce the step with a story.” After rifling through the materials in front of her, she handed two pages to Mr. Grow.

“Back to Calvin,” he said.

“Right. In this portion of the story, he conducts a fair test. Go ahead and read it. Then we’ll talk it over.”

In this short instructional story, Calvin learns about the engineering design process. These pages focus on conducting a fair test.

After he finished reading, Mr. Grow looked up. “In the previous part of the story,” he said, “Calvin identified a failure point.”

“Correct. Unfortunately, paper was falling out of the guinea pig cage.”

“So he brainstormed ideas to fix it. Then he chose the most promising solution.”

Ms. Sneed nodded. “Calvin’s mom suggested that he fix two things, but he says no. Fortunately, his teacher has trained him well. Calvin knows that you can only control one variable at a time.”

“And I love the way he rattles off the terminology,” Mr. Grow said. “Moving the plywood is the independent variable. All other variables are controlled.”

Again, Ms. Sneed nodded. “Also, Calvin mentions two other important scientific practices: measurement and replication. Both are important in conducting a fair test.”

Conducting a Fair Test – An Engineering Design Process

Next, Ms. Sneed pulled out two more pages. “Since this part of the engineering design process is more sophisticated, we’ll use these pages for direct instruction. At the top of this first sheet, kids clearly see that they should manipulate only one variable at a time. Below, they see the strategies used when conducting a fair test:

  • Identify failure points.
  • Control.
  • Compare.
  • Measure.
  • Replicate.
  • Repeat.

“On the second sheet, vocabulary for conducting a fair test is spelled out. For example, independent variable means the one thing you’re changing.”

“Very handy,” Mr. Grow replied.

Two reference guides help kids with steps and vocabulary for conducting a fair test.

Teaching Steps of the Engineering Design Process Through Earth Science Activities

Finally, Ms. Sneed opened her laptop. “As you know, after the story, we’ll work with a set of engineering design materials related to reducing impacts of earth processes on humans. That way, we integrate a science topic.”

As she scrolled through the resource, she reviewed earlier activities.

“In this first activity, kids considered an issue with a farmer’s field. Then they defined the problem. In addition, they identified criteria and constraints.

“For the second lesson, they analyzed a problem experienced by a town at the bottom of an active volcano. After that, they brainstormed possible solutions.”

Identifying the Strategies Used When Conducting a Fair Test

When she got to some pages titled “The Crumbling Road,” Ms. Sneed stopped scrolling.

“In this activity,” she said, “kids analyze a completed lab report involving a mountain road. After reading the report, they focus on Step 8, which is all about conducting a fair test. Then they answer the questions here. As you can see, they must list independent, controlled, and dependent variables. Additionally, they list measurement tools that would be used. Finally, they consider how these strategies made the test fair.”

Mr. Grow sat back in his chair. “Wow, this is powerful. For one thing, kids are forced to think about and identify conditions. And for another, they’re viewing an exemplar. Now they’ll know how their own lab sheet should look.”

A small smile spread across Ms. Sneed’s face. “I like the way you’re thinking,” she said.

In this activity, kids study a lab sheet and identify strategies used when conducting a fair test in the engineering design process.

Conduct a Fair Test in Every Engineering Design Project

“For the final activity in this earth science set,” Ms. Sneed continued, “kids will work through all of the steps in the engineering design process to build an earthquake-proof skyscraper.”


Ms. Sneed scrolled down a bit more and pointed to the lab sheet. “For each engineering design challenge, my lab sheets include this.” She pointed to the section for conducting a fair test.”

When conducting a fair test, kids must name one thing they will improve (independent variable) and many things they will keep the same (controlled variables). Then they build a new prototype and test it.

Once again, Ms. Sneed clicked away on her laptop. “Let’s look at the final engineering design standard from the NGSS.”

3-5-ETS1-3 Plan and carry out fair tests in which variables are controlled and failure points are considered to identify aspects of a model or prototype that can be improved.

“If the Next Generation Science Standards say that kids should do it, it must be important,” Mr. Grow said.

Enjoy Teaching

Ms. Sneed nodded. “As you know, hands-on learning makes me enjoy teaching. Furthermore, when we take the time to carefully plan instruction, kids really learn. Seeing that gives me a ton of fulfillment. But what seals the deal is knowing that I’ve addressed the intent of the standards.”

With a little laugh, she added, “That lets me sleep at night.”

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