Data Representation in Science (ACT Science)

Understanding Graphs and Charts

The ACT Science section is heavily focused on reading and interpreting visual representations of data. Success depends on quickly extracting information from graphs, tables, and diagrams.

Types of Graphs

1. Line Graphs

Shows: Continuous change over time or across a range

Key features:

• X-axis: Independent variable
• Y-axis: Dependent variable
• Line shows trend/pattern
• Multiple lines can compare groups

Example interpretation: Graph shows temperature (y-axis) vs. time (x-axis)

Questions might ask:

• "At 30 minutes, what was the temperature?" (Read directly from graph)
• "Between which times did temperature increase fastest?" (Look for steepest slope)
• "What was the overall trend?" (Increasing, decreasing, constant)

Reading strategies: ✓ Check axis labels and units
✓ Note scale (linear vs. logarithmic)
✓ Identify highest/lowest points
✓ Spot trends (increasing, decreasing, leveling off)

2. Bar Graphs

Shows: Comparisons between categories

Key features:

• Categories on x-axis
• Values on y-axis
• Height of bar = value
• Easy to compare

Example interpretation: Bar graph shows average rainfall by month

Questions might ask:

• "Which month had the most rainfall?" (Find tallest bar)
• "How much more rain fell in April than in June?" (Subtract bar heights)
• "What was the total rainfall for spring months?" (Add March + April + May)

Reading strategies: ✓ Read category labels carefully
✓ Note y-axis scale
✓ Compare bar heights
✓ Look for patterns across categories

3. Scatter Plots

Shows: Relationship between two variables

Key features:

• Each point = one observation
• Both axes show numerical data
• Pattern reveals correlation
• May include trend line

Correlation types:

• Positive: Points go up-right (both variables increase together)
• Negative: Points go down-right (one increases as other decreases)
• None: No clear pattern

Example interpretation: Scatter plot: Study hours (x) vs. test scores (y)

Questions might ask:

• "As study hours increased, test scores:" (Identify trend)
• "Which data point represents the student who studied 5 hours?" (Find x = 5)
• "Is there a relationship between study hours and test scores?" (Look for correlation)

Reading strategies: ✓ Look for overall pattern
✓ Identify outliers (points far from pattern)
✓ Note clusters of points
✓ Check if trend line is included

4. Pie Charts

Shows: Parts of a whole (percentages)

Key features:

• Circle = 100%
• Each slice = category
• Size shows proportion

Reading strategies: ✓ Add up slices (should = 100%)
✓ Compare relative sizes
✓ Look for largest/smallest categories

Tables and Data Sets

Reading Tables Efficiently

Table structure:

• Row headers (left)
• Column headers (top)
• Data cells (intersection)

ACT strategy:

1. Read headers first — know what table shows
2. Note units (°C, grams, meters, etc.)
3. Look for patterns (increasing, decreasing)
4. Find specific values by tracing row + column

Example table:

| Temperature (°C) | Pressure (kPa) | Volume (L) | |-----------------|----------------|------------| | 20 | 101 | 5.0 | | 40 | 115 | 5.5 | | 60 | 128 | 6.0 |

Question: "What was the pressure at 40°C?"

Strategy: Find row where Temperature = 40, read Pressure column → 115 kPa

Identifying Trends in Tables

Look for:

• Values increasing consistently
• Values decreasing consistently
• Proportional relationships
• Inverse relationships

Example: In table above:

• As temperature ↑, pressure ↑ (direct relationship)
• As temperature ↑, volume ↑ (direct relationship)

Interpreting Complex Visuals

Multi-Line Graphs

Shows: Multiple data series on same axes

Reading strategy:

1. Check legend (which line is which)
2. Compare lines (do they follow same trend?)
3. Find intersections (where lines cross)
4. Note differences between lines

Common ACT question: "According to the graph, Plant A grew faster than Plant B during which time period?"

Strategy: Find where Plant A line is steeper than Plant B line

Graphs with Multiple Y-Axes

Sometimes: Left y-axis measures one variable, right y-axis measures another

Critical: Check which line uses which axis!

Example:

• Left y-axis: Temperature (°C)
• Right y-axis: Pressure (kPa)
• Blue line uses left axis
• Red line uses right axis

Don't: Read blue line values from right axis — wrong units!

Logarithmic Scales

What: Each tick mark represents 10× previous value (not equal intervals)

Why used: To show data spanning many orders of magnitude

Reading strategy:

• Each step up multiplies by 10
• Distance from 1 to 10 = same as 10 to 100

ACT tip: Usually clearly labeled "log scale"

Common Data Representation Questions

Type 1: Direct Reading

"According to Figure 1, what was the pH at 30 minutes?"

Strategy:

1. Find Figure 1
2. Locate x = 30 minutes
3. Read y-value at that point
4. Check units!

No calculation needed — just read accurately

Type 2: Trend Identification

"Based on the graph, as altitude increased, air pressure:"

Choices: A. increased only
B. decreased only
C. increased then decreased
D. remained constant

Strategy:

1. Look at overall pattern of line/data
2. Left to right: going up, down, or flat?
3. Choose matching description

Type 3: Comparison

"Which trial had the highest concentration of Product X?"

Strategy:

1. Find Product X data (could be in table, graph, or chart)
2. Compare all trial values
3. Identify maximum

Tip: Fastest approach is visual — find tallest bar, highest point, largest number

Type 4: Calculation

"What was the average temperature over the three trials?"

Strategy:

1. Find all three temperature values
2. Add them up
3. Divide by 3

Note: These are less common than direct reading questions

Type 5: Extrapolation

"If the trend continued, what would the value be at X?"

Strategy:

1. Identify the trend (linear, exponential, etc.)
2. Extend the pattern
3. Estimate value at new point

Warning: Only extend slightly beyond data — don't make wild leaps!

Reading Diagrams

Experimental Setup Diagrams

Purpose: Show how experiment was conducted

What to identify:

• Equipment used
• How parts are connected
• What's being measured
• Controls and variables

ACT questions:

• "Which equipment measured temperature?" (Find thermometer in diagram)
• "Where was the pressure sensor located?" (Look for sensor)

Process Diagrams

Purpose: Show steps or cycles

Example: Water cycle, food web, energy flow

Reading strategy:

1. Follow arrows (show direction/flow)
2. Read labels on each step
3. Understand sequence

Common Mistakes to Avoid

❌ Misreading axis labels
Always check what each axis represents and units used!

❌ Wrong scale
Note if scale is by 1s, 5s, 10s, 100s, etc.

❌ Confusing lines in multi-line graphs
Check legend carefully

❌ Reading wrong axis on double-axis graphs
Match line color/style to correct axis

❌ Not noticing units
10 meters ≠ 10 centimeters!

❌ Extrapolating too far
Don't assume trends continue indefinitely

❌ Using outside knowledge
Answer based on the data shown, not what you think should happen

Quick Tips for ACT Data Representation

✓ Read axis labels first — Know what you're looking at
✓ Check units — Matters for correct answer
✓ Use a straight edge — Helps read graphs accurately
✓ Start at the axes — Trace to find intersection
✓ Compare visually — Often faster than calculating
✓ Look for patterns — Increasing, decreasing, constant
✓ Note outliers — Points that don't fit pattern
✓ Read questions carefully — Looking for max, min, average, range?
✓ Use process of elimination — Rule out obviously wrong choices
✓ Don't overthink — Most answers are direct reading

Practice Approach

For Data Representation passages:

1. Skim all figures first (10-15 seconds)

   • How many graphs/tables?
   • What do they show?

2. Read introduction (if short)

   • Sets context for data

3. Go straight to questions

   • Most can be answered by looking at specific figure

4. For each question:

   • Identify which figure has the answer
   • Locate specific data point or trend
   • Read directly from visual
   • Double-check units

5. Don't read entire passage deeply

   • Wastes time
   • Questions tell you where to look

Time-saving tip: You usually don't need to understand WHY the data looks the way it does — just need to read it accurately!

Remember: Data Representation is typically the easiest passage type on ACT Science. These are straightforward reading questions — no complex reasoning required. Master the skill of quickly extracting information from visuals, and you'll breeze through these sections!