Interpretation of Data
Reading tables and graphs, finding trends and interpolating or extrapolating values.
What it tests
Interpretation of Data questions ask you to read tables and graphs: find a value, spot a trend, compare two variables, and predict values between or beyond the data points. You almost never need outside science knowledge — the answer is in the figure.
How it shows up
- The Science test is 40 questions in 40 minutes — one minute per question. On the enhanced ACT it is optional: it isn’t part of your composite (English + Math + Reading), but it gets its own score and counts toward the STEM score, and many colleges still like to see it. Passages show data (tables and graphs), describe experiments, or present competing viewpoints.
- Interpretation of Data is the largest Science category — close to half of the questions.
- Typical stems: “According to Table 1, at 40°C…”, “As X increased, Y…”, “Based on Figure 2, if the trend continued, at 100°C Y would most likely be…”.
Key rules & concepts
The content you actually need to know.
Read the labels first
- Before the numbers: read the title, column headers or axis labels, and units.
- Check the key/legend when a graph has more than one line or bar.
- Watch for units that change between figures (mL vs. L, g vs. kg, seconds vs. minutes).
Finding values
- Table: find the row and the column, and read the cell where they meet.
- Graph: go across the x-axis to the value, straight up to the line, then straight across to the y-axis.
Trends
- Direct: as one variable increases, so does the other.
- Inverse: as one increases, the other decreases.
- Other patterns: increases then levels off; increases then decreases; no clear relationship.
- Check EVERY data point before calling a trend “always increases.”
Interpolation and extrapolation
- Interpolate: estimate a value BETWEEN two data points — the answer lies between their y-values.
- Extrapolate: estimate a value BEYOND the data by extending the trend.
- Ranges in the answer choices (“between 24 and 38”) are a gift: you only need to know which interval the value falls in.
Quick math with data
- Differences (how much did it increase?), ratios (about how many times as large?), and averages.
- “Approximately” means estimate — round and move on.
Strategy & traps
Step by step
- 1Skip the long introduction at first. Go to the question and find the figure it names.
- 2Circle the variables in the question and locate them on the table or axes.
- 3Read the exact values or the trend you need.
- 4Match to the answer choices; for predictions, extend the pattern.
Wrong series
On a graph with three lines, make sure you’re reading the one the question names.
Outside knowledge
If the data disagrees with what you remember from class, trust the data.
Units
A choice in the wrong unit (or off by 1,000) is a deliberate trap.
Worked examples
Try each one first, then reveal the solution.
Table 1: Time for 10 g of sugar to dissolve in 200 mL of water
| Water temperature (°C) | Dissolving time (s) |
|---|---|
| 20 | 96 |
| 40 | 61 |
| 60 | 38 |
| 80 | 24 |
Example 1
According to Table 1, as the water temperature increased, the dissolving time:
- Aincreased only.
- Bdecreased only.
- Cincreased, then decreased.
- Dstayed the same.
Example 2
Based on Table 1, the dissolving time at 50°C would most likely be closest to:
- A30 s
- B50 s
- C70 s
- D90 s
Example 3
If the trend in Table 1 continued, the dissolving time at 100°C would most likely be:
- Aless than 24 s.
- Bbetween 24 s and 38 s.
- Cbetween 38 s and 61 s.
- Dgreater than 96 s.
Practice
Pick an answer for instant feedback. Answers lock once chosen.
Table 2: Average height (cm) of bean seedlings grown under three colors of light
| Day | Red light | Blue light | Green light |
|---|---|---|---|
| 0 | 0.0 | 0.0 | 0.0 |
| 5 | 2.1 | 2.8 | 1.2 |
| 10 | 5.4 | 6.9 | 2.9 |
| 15 | 8.2 | 10.3 | 4.1 |
| 20 | 10.1 | 12.6 | 4.8 |
Question 1
According to Table 2, on Day 10, which group of seedlings had the greatest average height?
Question 2
From Day 15 to Day 20, the average height of the seedlings under red light increased by about:
Question 3
Based on Table 2, which statement about the seedlings under green light is true?
Question 4
If the blue-light seedlings kept growing at the same rate they did from Day 15 to Day 20, their average height on Day 25 would most likely be:
Question 5
On Day 20, the average height under blue light was approximately how many times the average height under green light?