TEAS Scientific Reasoning: Experiments and Variables
Updated October 27, 2026
Part of the ATI TEAS 7 Science section tests scientific reasoning: understanding how experiments are designed and what data show. These questions don’t need memorized facts, just a clear method. Here it is, followed by free practice questions.
The scientific method
- Ask a question.
- Form a hypothesis: a testable prediction.
- Design an experiment.
- Collect and analyze data.
- Draw a conclusion: does the data support the hypothesis?
Variables
| Term | Meaning | Example: does fertilizer affect plant height? |
|---|---|---|
| Independent variable | What the experimenter changes | Amount of fertilizer |
| Dependent variable | What is measured | Plant height |
| Controlled variables | What is kept the same | Light, water, soil, plant type |
| Control group | The group that doesn’t get the treatment | Plants with no fertilizer |
Reading data
- In a graph, the independent variable is usually on the x-axis and the dependent variable on the y-axis.
- A correlation between two things doesn’t prove that one causes the other.
- A conclusion should only claim what the data actually show.
Free scientific reasoning questions
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A researcher tests whether different amounts of caffeine affect reaction time. What is the dependent variable?Answer: AThe dependent variable is what's measured, here reaction time. The amount of caffeine is the independent variable.
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In an experiment on a new fertilizer, which group is the control group?Answer: BThe control group doesn't receive the treatment, so it gives a baseline to compare against.
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Which is a testable hypothesis?Answer: CA hypothesis must be a testable prediction. Only this statement can be measured and checked with an experiment.
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A study finds that people who carry lighters are more likely to get lung cancer. What is the best conclusion?Answer: DCorrelation isn't causation. A third factor, smoking, explains both.
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On a graph of plant height against weeks of growth, where is time usually placed?Answer: ATime, the independent variable here, usually goes on the horizontal x-axis, and the measured result goes on the y-axis.
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Why should only one variable be changed at a time in an experiment?Answer: BChanging one variable while keeping others the same lets you tell which factor caused the result.
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