A fair test changes the factor being investigated while keeping other relevant conditions the same. Here the intended difference is wheel size. If a ramp or a cart’s mass also changes, that gives another possible explanation for the result. The recorded numbers are invented examples for checking the test design. Experimental design links a causal question to interventions, measurements and control of competing influences. Confounding occurs when a second change remains associated with the intended factor, preventing a clean attribution. Our simplified cart table makes selected variables explicit, but it neither represents every real influence nor establishes a general rule from invented trial outcomes.
Engineering and scientific investigation · Discover & try
How can a comparison isolate one changed factor?
Reading level 5 of 5 · AdvancedChange
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Independent variable
The factor deliberately changed.
Dependent variable
The outcome measured in a test.
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See how it works
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Invented cart outcomes illustrate experimental design. The shown variables do not cover every real influence, and the activity is entirely virtual.
What to look for
- Ramp and mass match, so the represented test isolates wheel size.
- The result now has another possible cause: the ramp changed too.
- Changing mass as well prevents a clean wheel-size conclusion.
Explain what you noticed
To compare light levels for two virtual plants, which plan best isolates light?
Keep this idea: Keep relevant conditions comparable so that the intended change can be interpreted.
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Source material checked 2026-10-29. Explanations and activities by Nepedia. Source links do not imply endorsement.
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