ACT Science: Understand Hypothesis Testing to Answer "What Would Support This?" Questions

A hypothesis is a testable prediction. Questions ask "Which observation would support this hypothesis?" or "What would refute this claim?" To answer, trace the logic: if the hypothesis is true, what must we observe? If the hypothesis is false, what would we see instead? Example hypothesis: "Increasing temperature increases enzyme activity." If true, we should observe enzyme activity rising as temperature rises. If false, we should see activity decrease or stay constant. Questions reward logical reasoning about what evidence would prove or disprove the hypothesis, not guessing based on science knowledge.

Another example: Hypothesis says "The drug reduces blood pressure." Supporting evidence: blood pressure drops in people taking the drug. Refuting evidence: blood pressure stays the same or increases. Questions often ask which observation would support the hypothesis; you predict the logical consequence, find it in the answer choices.

Mistake 1: Confusing "would support" with "would prove." Supporting evidence makes the hypothesis more likely, but doesn't prove it absolutely. Be careful with extreme language. Mistake 2: Using real-world science knowledge instead of passage logic. The passage defines the hypothesis in a specific way; use that definition, not your general science knowledge. Mistake 3: Picking an observation that's related to the topic but doesn't directly test the hypothesis. The observation must have a direct logical connection to the hypothesis, not just be on the same topic.

During practice, write out the hypothesis in simple terms, then predict what observation would logically support or refute it. Compare your prediction to the answer choices.

Hypothesis 1: "Sunlight intensity affects plant growth rate." Supporting evidence: Growth rate increases with sunlight. Refuting evidence: Growth rate stays the same regardless of sunlight. Hypothesis 2: "Cold temperatures slow bacterial reproduction." Supporting evidence: Fewer bacteria in cold conditions. Refuting evidence: Same number of bacteria at all temperatures. Hypothesis 3: "Acidic soil reduces crop yield." Supporting evidence: Lower yield in acidic soil. Refuting evidence: Same yield in acidic and neutral soil. For each hypothesis, identify the predicted outcome if it's true and what would contradict it. This logic train prepares you for questions asking what evidence would support or refute hypotheses.

Find three hypothesis testing questions from a practice test. For each, predict supporting and refuting evidence before looking at choices. By the third question, logical prediction will feel intuitive.

Hypothesis and prediction questions make up 15-20% of ACT Science. They test reasoning about evidence and causation rather than knowledge of science facts. Students who develop logical hypothesis-testing skills pick up 1-2 points on the science section because they can reason through questions without needing specialized knowledge.

Use the prediction method on your next practice test. For every hypothesis question, trace the logic: if true, what would we see? If false, what would we see? By test day, these questions should reward your reasoning ability, not lucky guesses.