Thinking Like an Experimenter
Research summary passages describe one or more experiments and ask you to understand their design and results. The key is to separate what was changed, what was measured, and what was held constant.
Identify the Variables
- •Independent variable: what the scientists deliberately change (for example, temperature).
- •Dependent variable: what they measure in response (for example, reaction rate).
- •Controlled variables: everything kept the same so the test is fair. Most design questions reward spotting these three roles.
The Purpose of a Control
A control group receives no treatment or a standard condition and serves as a baseline for comparison. If a question asks why a control was used, the answer is almost always "to provide a comparison" or "to isolate the effect of one variable."
Compare Across Experiments
Many passages run several experiments that differ in one way. Ask what changed from Experiment 1 to Experiment 2; that difference usually explains the different results. Watch for a variable that appears in one study but not another.
Predict and Extend
Questions may ask what would happen if a value were pushed higher or lower. Use the trend already shown in the data and continue it logically.
Read Methods, Not Just Results
The procedure paragraphs tell you how the data were produced. When a question asks about how an experiment was conducted, the answer lives in the methods, not the graph.
Key Takeaways
- •Separate independent, dependent, and controlled variables.
- •A control group exists to provide a fair baseline.
- •The one thing that differs between experiments explains differing results.
- •Extend established trends to predict new outcomes.
