ACT Science Practices: Data Interpretation, Experimental Design, and Evaluation
What this domain tests
This domain covers the skills applied across all passage types: interpreting graphs and tables, evaluating experimental design, comparing and combining results, and judging the strength of competing explanations.
Core practices
Graph and table reading. Identify the variables on each axis, note units, and describe the relationship (increasing, decreasing, linear, curved, plateau). Compare values across columns or curves. When asked to interpolate, stay between known points; when extrapolating, extend the observed pattern cautiously.
Experimental design. Determine which variable was manipulated and which was measured. Identify what was held constant so that a result can be attributed to the manipulated variable. Recognize that a valid comparison requires a control or baseline condition.
Synthesis across figures. Many questions require combining two figures: for example, using a table to find a condition and a graph to read the outcome under that condition.
Evaluating viewpoints. Decide which new observation would support or undermine a claim. An observation that both sides predict does not distinguish them; a discriminating observation does.
Traps
- Assuming a cause when the passage only shows an association.
- Treating a single trial as conclusive when the passage notes variability.
- Extending a trend beyond the range of data without justification.
- Picking a choice that is plausible science but not supported by the given results.
Rule of thumb
State the relationship in one sentence before answering: "As X increases, Y increases until Z, then levels off." Then test each choice against that sentence.
Worked example: Two experiments differ only in temperature, and outcomes differ. Because temperature is the only changed variable, the difference in outcome is best attributed to temperature.