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ACT Science reporting category

ACT Evaluation of Models and Results Practice

Evaluation of Models and Results questions ask you to judge whether data support a hypothesis, conclusion, or model, and to compare competing explanations of the same observations. According to ACT, this category makes up 24–38% of scored science questions.

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24–38% of scored Science questions3 original questionsInstant answer checks

At a glance

Evaluation of Models & Results on the ACT: the key numbers

Section and category facts from ACT.org, checked October 9, 2026. Time per question is ACT's section time divided by its question count.
SectionACT Science: 40 questions in 40 minutes
Scored questions34 scored, 6 field test
Reporting categoryEvaluation of Models & Results
Share of scored questions24–38%, according to ACT
Average time per questionAbout 60 seconds
Counts toward the CompositeNo, Science is optional
Practice on this page3 original questions: Easy, Medium, Hard

What this tests

What does ACT Evaluation of Models & Results test?

Practice questions

Practice ACT Evaluation of Models & Results questions

Pick an answer to check it. Each question has one correct choice.

Question 1 of 3Easy

Brine shrimp are tiny animals that live in salty lakes. A student hypothesized that the percentage of brine shrimp eggs that hatch would increase as the salinity (salt concentration) of the water increased from 10 g/L to 50 g/L.

To test this hypothesis, she placed 100 eggs in each of five containers of water with different salinities. All containers were kept at 26°C under the same light. After 48 hours, she counted the hatched eggs in each container.

Brine shrimp eggs hatched after 48 hours
Salinity (g/L)Eggs hatched (%)
1042
2071
3088
4064
5030
Do the results support the student's hypothesis?
Show answer and explanation
Correct answerC. No; the hatching percentage decreased as salinity increased above 30 g/L.

How to solve it

  1. The hypothesis predicts that hatching rises across the whole range, from 10 g/L to 50 g/L.
  2. Hatching rose from 42% to 88% between 10 and 30 g/L, then fell to 64% at 40 g/L and 30% at 50 g/L.
  3. The drop above 30 g/L contradicts the hypothesis, so the answer is No, choice C.
Why the other choices miss
A is false: 50 g/L had the lowest hatching percentage, 30%. B is false because hatching fell after 30 g/L. D gives the right verdict for a false reason: 30 g/L had the highest hatching percentage, 88%, not the lowest.
Question 2 of 3Medium

Over 3 years, the water level of a small lake fell by 1.2 m. Two scientists offered explanations.

Scientist 1: The drop was caused mainly by increased evaporation. Average summer air temperatures near the lake were higher during these 3 years than in earlier years, and warmer water evaporates faster. Rainfall stayed about the same as in earlier years.

Scientist 2: The drop was caused mainly by water seeping out through new cracks in the lake bottom. A small earthquake struck the area just before the water level began to fall. Evaporation increased only slightly and is too small to explain a 1.2 m drop.

Which of the following findings, if true, would most strengthen Scientist 2's explanation?
Show answer and explanation
Correct answerA. The lake's water level also fell during the winter months, when evaporation from the lake is very low.

How to solve it

  1. Scientist 2 needs evidence that water left the lake in a way evaporation cannot explain.
  2. If the level kept falling in winter, when evaporation is very low, something other than evaporation was removing water, such as seepage through cracks.
  3. That finding supports Scientist 2 and not Scientist 1, so the answer is A.
Why the other choices miss
B supports Scientist 1, whose explanation depends on warmer summers. C fits both views, since neither scientist blames rainfall. D weakens Scientist 2: a lake without cracks losing the same amount points to a cause both lakes share, such as weather.
Question 3 of 3Hard

Students burned four samples in open dishes and measured the mass of the solid left in each dish after burning was complete.

Student 1: Burning destroys part of a substance's matter as it gives off heat and light. So the solid left after burning always has less mass than the original sample.

Student 2: Burning combines a substance with oxygen from the air. Matter is not created or destroyed: the products have the same total mass as the original sample plus the oxygen used. The solid left behind gains mass when the products stay solid and loses mass when most products escape as gases.

Mass of each sample before and after burning in an open dish
SampleMass before burning (g)Mass of solid after burning (g)
Steel wool5.005.85
Magnesium ribbon0.500.82
Paper5.000.25
Wood splint4.000.08
Suppose a 0.50 g magnesium ribbon were burned inside a sealed flask holding enough air for complete burning. Student 2 would most likely predict that the total mass of the flask and everything inside it would:
Show answer and explanation
Correct answerB. stay the same.

How to solve it

  1. In the open dish, the magnesium's solid gained 0.82 - 0.50 = 0.32 g. Student 2 explains that gain as oxygen taken from the air.
  2. In a sealed flask, that oxygen is already inside, so its mass is already part of the starting total.
  3. Student 2 says matter is not created or destroyed, so oxygen moving from the air into the solid leaves the total unchanged: choice B.
Why the other choices miss
A counts the oxygen's mass twice; it was already inside the flask before burning. C and D both have matter disappearing, which matches Student 1's view, while Student 2 says matter is not destroyed. D would also mean the whole ribbon vanished.

Avoid these traps

What mistakes do students make on Evaluation of Models & Results?

Answering from your view

When a question asks what Scientist 2 would predict, the answer follows Scientist 2's stated model, even if another model seems more correct to you.

Fix: Reread that scientist's paragraph and apply only the rules it states.

Right verdict, wrong reason

Yes or No choices often pair a correct verdict with a false or irrelevant reason. Choosing by the verdict alone can still lose the point.

Fix: Check the reason against the data before choosing; both halves of the choice must be true.

Counting neutral facts as support

A finding that both explanations already accept does not strengthen either one, even when it is true and on topic.

Fix: Ask whether the finding would surprise one view but not the other. If it would not, it is neutral.

Study method

How should you practice ACT Evaluation of Models & Results?

  1. Before the questions, summarize each viewpoint or hypothesis in one short line in your own words.
  2. Note what each explanation predicts and what evidence it relies on.
  3. For support or weaken questions, test each choice: would this finding be more likely if that view were true?
  4. For Yes or No questions, check that both the verdict and the reason match the data.
  5. Practice two-viewpoint sets in Dolphin, and after each one, write which sentence in the passage decided the answer.
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FAQ

Questions about ACT Evaluation of Models & Results

Does ACT Science count toward the Composite score?

No. The Composite is the average of English, math, and reading, and science is an optional add-on that does not affect it. ACT began phasing science out of the Composite for National online testing in April 2025, and since September 2025 all ACT tests use the updated calculation. Students who take science also receive a STEM score, the average of math and science.

How much of ACT Science is Evaluation of Models and Results?

According to ACT, Evaluation of Models and Results makes up 24–38% of scored science questions. ACT lists the other two science categories as Interpretation of Data, at 38–50%, and Scientific Investigation, at 18–32%.

How do I handle questions that compare two scientists?

Read each viewpoint and write a one-line summary of its main claim and its evidence. For each question, note which viewpoint it asks about before reading the choices. A common error is applying sound reasoning to the wrong scientist.

Do I have to decide which scientist is right?

Only if the question asks. A question about what Scientist 1 would predict is answered from Scientist 1's stated view, even if you find Scientist 2 more convincing. Read the question for whose view it names.

Can I see my results for this category after the test?

Yes. The ACT score report lists each reporting category with questions on your test, along with your number correct and percent correct. Compare your percent correct across the science categories to choose what to practice next.

Related practice

ACT Interpretation of Data PracticeACT Scientific Investigation PracticeACT Integration of Knowledge and Ideas PracticeAll ACT Science practiceACT English practiceACT Math practiceACT Reading practiceDolphin ACT prepSAT vs ACTCollege ACT score ranges

Sources

Where these facts come from

ACT facts checked . Every practice question on this page is original Dolphin practice written to match one ACT reporting category. None is a released ACT item.

ACT® is a trademark registered by ACT, Inc., which is not affiliated with, and does not endorse, Dolphin.