ACT Science reasoning skills: a complete guide to the three reporting categories, question types, evaluation, outside knowledge, and translating data

Why reasoning skills sit underneath every question

Whatever the passage format, every ACT Science question tests one of three reasoning skills, and knowing the skill tells you how to answer. This guide ties together the matching dot-point pages, each with its own practice: Interpretation of Data question types, Scientific Investigation question types, evaluating models and inferences, the outside-knowledge questions, and translating between graphs and text.

Interpretation of Data: read the figure

The largest category. Four recurring question types:

• Read a value: a number at a given point (check axes and units, then read).
• Name a trend: direction (up, down, flat) and rate (steady or changing).
• Compare: which is larger, by how much, or where two are equal.
• Interpolate or extrapolate: estimate between or beyond data points.

The common error is naming the direction correctly but missing whether the rate is constant or changing.

Scientific Investigation: read the method

Answered from the method. Three types:

• Identify: the independent, dependent, and controlled variables and the control group.
• Explain a step: why a variable is controlled (removes a confounder), why a control group exists (baseline), why a measurement repeats (reliability).
• Modify or extend: add trials along the tested variable; avoid changes that introduce a new uncontrolled variable.

Evaluation: match the claim to the evidence

Accept only what the data justify.

• A supported conclusion stays within the group and range studied and claims only what was measured.
• A hypothesis is consistent only if the result fits throughout, not just in part.
• Reject overgeneralisation, unmeasured claims, and correlation read as causation.

Outside knowledge: the rare exception

A handful of questions (about five to eight) need a basic high-school fact, recognisable because the answer is not on the page. Keep a light core ready: water freezes at 0 and boils at 100 degrees Celsius; lower pH is more acidic; plants take in carbon dioxide and release oxygen; density is mass over volume. Do not over-study content, since most questions are answered from the figures.

Translating data

Match a description or table to the right graph by checking shape and key points:

• Turn each phrase into a feature: "increased" rises, "leveled off" flattens, "peaked then fell" is up-then-down, a changing rate is a curve.
• For a table, equal steps mean a straight line; growing or shrinking steps mean a curve.
• Confirm the start, peak, and end match.

How these skills are examined

• Interpretation of Data: read values, name trends with their rate, compare, interpolate or extrapolate.
• Scientific Investigation: identify design elements, explain a step's purpose, modify or extend the design.
• Evaluation: judge conclusions and hypotheses against the evidence and reject over-reach.
• Outside knowledge: recognise the rare fact-based question and supply a basic fact.
• Translation: match words and tables to graphs by shape and key points.

Check your knowledge

A quick check on the reasoning skills. Answer them, then read the solutions.

1. Name the four Interpretation of Data question types. (2 points)
2. From where are Scientific Investigation questions answered, and what is the purpose of a controlled variable? (2 points)
3. A study tested adults aged 40 to 60. Which conclusion is supported and which is an over-reach? (2 points)
4. How do you recognise an outside-knowledge question? (2 points)
5. A table's values rise by 2, then 4, then 8. Straight line or curve, and which way? (2 points)