What do Interpretation of Data questions look like, and how do you answer each kind?
Interpretation of Data question types on ACT Science: reading a value, identifying a trend, comparing data points, and interpolating or extrapolating, each answered straight from the figure.
A focused answer on the Interpretation of Data question types on ACT Science: reading an exact value, naming a trend, comparing two data points, and interpolating or extrapolating, with the figure-first method for each and why this category carries the most points.
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What this topic is asking
Interpretation of Data is the largest ACT Science reporting category, so knowing its question types and a method for each is the highest-leverage preparation you can do. Almost every one of these questions is answered straight from a figure: a graph, a table, or a diagram. This page sorts the category into its recurring types and gives a clean approach to each.
Type 1: read a value
The simplest and most common type asks for a specific value: the temperature at which a rate peaked, the population at a given hour, the solubility at a stated temperature.
- Check the axes and units.
- Go to the point the question names and read the value, going up to the curve and across, or to the row-and-column intersection in a table.
These are quick points; the only risk is misreading the axis or the gridline spacing, so the discipline is to confirm the axes first, as in reading line graphs and trends.
Type 2: name a trend
A trend question asks how one variable changes as another changes. Beyond the basic three (direct, inverse, no relationship), the ACT often tests the rate of change:
- Steady (linear) increase: equal steps each interval.
- Accelerating increase: larger steps each interval (the curve bends upward).
- Decelerating increase or a peak: smaller steps, then a turn.
Noticing whether the rate is constant or changing is a frequent distinction, as in a population that quadruples each interval (accelerating) versus one that adds a fixed amount (steady).
Type 3: compare data points
A comparison question asks which value is larger, by how much, or where two are equal.
- For "which is larger," read both values and compare.
- For "by how much," read both and subtract.
- For "where are they equal," find the point where two curves cross or two columns match.
The arithmetic is light; the care is in reading the two correct values (and the right lines on a multi-line graph) before comparing.
Type 4: interpolate or extrapolate
These ask you to estimate a value not directly given:
- Interpolation: between known points, by following the trend (a midpoint is about the average for a steady trend).
- Extrapolation: beyond the known points, by continuing the pattern (less certain).
The full method is in interpolation and extrapolation; here it is one of the four Interpretation of Data types to recognise on sight.
Why this category dominates
Interpretation of Data is the biggest slice of the section, so these four types appear again and again. The good news is that they are the most mechanical: with the axes checked and the figure read carefully, the answer is on the page. Investing practice in fast, accurate figure reading pays off across the whole section, including the data questions that appear inside Research Summaries and even Conflicting Viewpoints passages.
Try this
Q1. A quantity rises by larger and larger amounts each interval. Is this a steady increase or an accelerating one, and how can you tell? [2 points]
- Cue. Accelerating; the step sizes grow each interval (the curve bends upward), unlike a steady increase, which adds the same amount each time.
Q2. Name the four recurring Interpretation of Data question types. [2 points]
- Cue. Read a value; name a trend (direction and rate); compare data points; interpolate or extrapolate.
Exam-style practice questions
Practice questions written in the style of ACT exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
ACT Science (style)1 marksA graph shows a bacterium's population over time: 100 at 0 h, 400 at 2 h, 1600 at 4 h. Between 0 and 4 hours, the population is best described as: (A) decreasing. (B) constant. (C) increasing, and at a growing rate. (D) increasing at a steady rate.Show worked answer →
A 1-point trend question that distinguishes types of increase.
The correct answer is (C). The population rises (100 to 400 to 1600), and the jumps grow larger (300, then 1200), so it increases at a growing rate, not a steady one. (A) and (B) contradict the data, and (D) misses that the increases accelerate. Interpretation of Data trend questions often test whether you notice the rate of change, not just the direction.
ACT Science (style)1 marksA table lists a metal's resistance: 10 ohms at 20 degrees Celsius and 14 ohms at 60 degrees Celsius, rising steadily. The best estimate of the resistance at 40 degrees Celsius is: (A) 8 ohms (B) 12 ohms (C) 14 ohms (D) 18 ohmsShow worked answer →
A 1-point interpolation question.
The correct answer is (B), 12 ohms. 40 degrees is halfway between 20 and 60 degrees, and resistance rises steadily from 10 to 14 ohms, so the midpoint estimate is ohms. (A) is below the range, (C) is the 60-degree value, and (D) is above it. Interpolation estimates a value between known points using the trend.
Related dot points
- Reading line graphs on ACT Science: locating the axes and units, finding a value at a given point, and naming a trend (direct, inverse, or no relationship) between two variables.
A focused answer on reading line graphs in ACT Science: checking the axes and units first, reading a value at a given point, and identifying whether two variables show a direct, inverse, or no relationship. The most points on the test come from this single skill.
- Reading tables on ACT Science: orienting to the rows, columns, and units, locating a value at an intersection, and tracking how one variable changes while another is held fixed.
A focused answer on reading data tables in ACT Science: orienting to the rows, columns, headers, and units, finding a value at a row-column intersection, and isolating the effect of one variable by holding others constant across a dense multi-variable table.
- Interpolation and extrapolation on ACT Science: estimating a value between known data points and extending a trend beyond the measured range, while flagging the greater uncertainty of extrapolation.
A focused answer on interpolation and extrapolation in ACT Science: estimating a value between two known data points by following the trend, and predicting a value beyond the measured range by extending it, plus why extrapolation is less certain and how the ACT tests both.
- The three ACT Science reporting categories - Interpretation of Data, Scientific Investigation, and Evaluation of Models, Inferences, and Experimental Results - and the skills and approximate proportions of each.
A focused answer on the three ACT Science reporting categories: Interpretation of Data (the largest), Scientific Investigation, and Evaluation of Models, Inferences, and Experimental Results. Covers the skills each one tests, their approximate proportions, and how recognising the category guides your answer.
- Translating data on ACT Science: matching a verbal description of a relationship to its graph, pairing a table with the graph that represents it, and converting between data forms by checking shape and key points.
A focused answer on translating data on ACT Science: matching a worded description of a relationship to the correct graph, pairing a table with the graph that represents it, and converting between forms by checking the overall shape and a few key points such as the start, the peak, and the end.
Sources & how we know this
- Description of the ACT Science Test — ACT, Inc. (2025)
- ACT Science Practice Test Questions — ACT, Inc. (2025)