ACT Science Research Summaries: experiments, variables and controls
Research Summaries passages describe one or more related experiments and their results, and the questions ask about how the experiments were designed and what the results show. ACT says this format is 50–56% of the Science section, the largest of the three. ACT's own tip is to look at the experimental design, including the controls and variables, because questions are likely to ask about it. In ACT's 2025–26 practice test there were four Research Summaries passages with six questions each, one of them unscored.
Where it shows up on the ACT
| Enhanced ACT | |
|---|---|
| Section | Science (optional) |
| Length | 40 questions (34 scored) in 40 minutes, about 60 seconds each |
| Reporting category | Research Summaries (one of three passage formats; ACT reports Science scores by skill category, not by format) |
| Share of the section | 50–56% of Science |
| In the Composite | No. Science gets its own 1–36 score and counts toward STEM. |
ACT gives format shares separately from its three reporting categories. In ACT's 2025–26 practice test we counted 4 Research Summaries passages of 6 questions each; one of the four was the unscored passage. Source: ACT, Preparing for the ACT 2025–2026, pp. 6–10: what each section covers and its reporting categories.
What the questions ask you to do
- Name the independent variable, the dependent variable and what was held constant.
- Explain why a control or a particular step was included.
- Pick an experiment that would test a new question.
- Say whether the results support a hypothesis or claim.
- Predict the result of an additional trial, or compare results across studies.
The experiment vocabulary you need
Questions use these words without defining them.
| Term | What it means | How to find it |
|---|---|---|
| Independent variable | What the researcher changed on purpose | The column or axis with chosen, evenly spaced values |
| Dependent variable | What was measured as a result | The values the researcher recorded |
| Controlled variable | Something kept the same in every trial | Often stated once in the procedure, like 'each dish received 10 mL of water' |
| Control group | A trial with no change, used for comparison | Words like 'no treatment', 'distilled water' or 'room temperature' |
| Hypothesis | A testable prediction | Usually stated before the results |
| Trial | One run of the experiment under one set of conditions | Rows in a results table |
If two things change between trials, the experiment can't show which one caused the difference.
Common mistakes
Wrong answer choices are often built around these.
- Mixing up the independent and dependent variables. Ask which one the researcher chose and which one they measured.
- Choosing an experiment that changes two things at once. A good test changes only the variable in question.
- Treating 'consistent with' as 'proves'. One study can support a claim without proving it.
- Missing the controlled variables in the procedure. They are often stated once, in a sentence before the table.
- Assuming a trend continues forever. If the last values level off or drop, the pattern has changed.
- Mixing results from different studies. Check which study's table a question refers to.
3 example questions with answers
Written by Ashore in the style of the enhanced ACT. They aren't official ACT questions. Try each one before you open the answer.
Question 1 · Easy
Study 1: Radish seeds sprouted after 3 days (20 seeds per dish, 10 mL of water, kept in the dark) Temperature (°C) Seeds sprouted 10 4 15 11 20 17 25 18 In Study 1, the independent variable was:
- Athe number of seeds that sprouted.
- Bthe temperature.
- Cthe amount of water.
- Dthe number of days.
Show the answer
B. The researcher chose four temperatures and recorded how many seeds sprouted at each, so temperature is what was changed on purpose. The number of seeds that sprouted is what was measured, and the water and the number of days were kept the same.
Question 2 · Medium
Study 1: Radish seeds sprouted after 3 days (20 seeds per dish, 10 mL of water, kept in the dark) Temperature (°C) Seeds sprouted 10 4 15 11 20 17 25 18 A student wants to find out whether light affects how many radish seeds sprout. Which of the following experiments would best test this?
- FFour dishes at 20°C with 10 mL of water each, two in light and two in the dark
- GFour dishes in the light, one at each temperature in Study 1
- HTwo dishes at 20°C in the light, one with 10 mL of water and one with 20 mL
- JTwo dishes in the dark, one at 10°C and one at 25°C
Show the answer
F. To test light, only light should change. Four dishes at the same temperature and water, half in light and half in the dark, do that. Putting every dish in the light changes temperature but not light, the 10 mL and 20 mL dishes test water, and two dark dishes at different temperatures repeat Study 1.
Question 3 · Hard
Study 2: Radish seeds sprouted after 3 days (20 seeds per dish, 20°C, kept in the dark) Water (mL) Seeds sprouted 5 6 10 15 20 17 40 9 A student claims that giving radish seeds more water always increases the number that sprout. Do the results of Study 2 support this claim?
- AYes, because more seeds sprouted at 10 mL than at 5 mL.
- BYes, because the most seeds sprouted at 20 mL.
- CNo, because fewer seeds sprouted at 40 mL than at 20 mL.
- DNo, because the temperature was not changed.
Show the answer
C. The claim says more water always helps, but going from 20 mL to 40 mL cut the number from 17 to 9, so the data contradict it. The rise from 5 mL to 10 mL and the peak at 20 mL are true but don't cover the whole range, and keeping temperature the same is what makes the test fair.
More ACT Science guides
- Data Representation passages
- Conflicting Viewpoints passage
- Science timing and tips
- ACT score calculator: questions right in each section to a 1–36 score and Composite.
- SAT vs ACT: which test fits you better.
- All ACT guides and free tools
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Practice test 1
Example
27
Composite
(28 + 26 + 27) ÷ 3
- English28
- Math26
- Reading27
- ScienceOptional, not in the Composite25