Investigation Design
Elementary School
Definition
The planning of a fair experiment, including identifying variables, choosing materials and steps, and deciding what to measure. A well-designed investigation changes only one variable at a time so results can be trusted.
Worked examples
Testing if fertilizer helps plants grow: keep light, water, and soil type the same; change only the amount of fertilizer.
Only one variable (fertilizer amount) changes so you know it caused any difference in growth.
Measuring how ramp angle affects a toy car's speed: use the same car, same surface, same starting position; change only the angle.
Controlling every variable except angle makes the test fair and the results trustworthy.
Common mistakes
- changing both the type of fertilizer and the amount at the same time → change only the amount, keeping the type constant Changing two variables means you cannot tell which one caused the result.
- forgetting to decide what to measure before starting the experiment → plan what data to collect (height, time, temperature) in the design phase Without a clear measurement plan, you may miss the data you need or collect the wrong thing.
- using different materials for each trial without recording them → use identical materials or record every difference as a variable Uncontrolled differences make it impossible to trust your conclusions.
Where you'll use it next
You'll use investigation design throughout science labs in biology, chemistry, and physics to set up fair tests, and later in science fair projects and real research where controlling variables is essential.
See also
Reviewed by Pat Cheng, M.Ed. — StudyPug Curriculum Lead · Last updated June 6, 2026