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Session 6 of 8
Trends and Patterns Over Time
Line graphs show how things change. Today we learn to read the story a line tells — and even predict what comes next.
📊 Data Science for Young Minds · Grade 4
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Opening Hook
Trace the Line — What Do You See?
Before seeing the labels, trace the line below with your finger.
● — ● — ● — ● ↗ ● ↗ ● ↗ ● ↗ ● ↘ ● ↘ ● ↘ ● — ●
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Is this going up or down? Where is the highest point? Now reveal: these are monthly temperatures!
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Today's Plan
What We're Doing Today
- 📈 Line graphs — what they are and how to read them
- 🔍 Trend vocabulary: rising, falling, steady, peak, dip
- 📊 Read 2 line graphs and answer trend questions
- ✏️ Build your own line graph from a data table
- 🔮 Interpolation vs. extrapolation — predicting from trends
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Lesson 1
What Is a Line Graph?
A line graph shows how a value changes over time. Time goes on the x-axis (horizontal), and the measured value goes on the y-axis (vertical).
- 📍 Each dot = one data point at one moment in time
- 📏 Dots are connected with lines to show change
- ⏰ The x-axis is always time (days, months, years, weeks)
- 📐 The y-axis is what we're measuring (temperature, books, sales)
The slope of the line tells you how fast something is changing. Steep = fast change. Gentle = slow change. Flat = no change.
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Lesson 2
Reading Trend Direction
The most important thing to identify in a line graph is the trend — the overall direction the data is moving.
📈
Increasing
Line goes upward — value is growing over time
📉
Decreasing
Line goes downward — value is shrinking over time
➡️
Steady
Line is roughly flat — value stays about the same
⚠️ One dip or spike doesn't change the overall trend. Look at the big picture — not just the last two points!
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Graph 1
Monthly Temperature — Reading the Trend
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|
| 32 | 35 | 45 | 55 | 65 | 75 | 82 | 80 | 72 | 60 | 48 | 36 |
- 🌡️ What month has the highest temperature?
- ❄️ What month has the lowest temperature?
- 📈 What is the trend from January to July?
- 📉 What is the trend from July to December?
- 📊 What is the temperature range across the year?
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Graph 2
Books Read Per Week — Reading the Trend
| Week 1 | Week 2 | Week 3 | Week 4 | Week 5 | Week 6 | Week 7 | Week 8 |
|---|
| 2 | 3 | 2 | 5 | 4 | 6 | 5 | 7 |
- 📚 What is the overall trend — increasing, decreasing, or steady?
- 📉 Week 3 dropped from Week 2. Does this mean the trend changed?
- 🔮 Based on the trend, how many books might be read in Week 9?
- 📊 What is the range of books read?
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Activity!
Build Your Own Line Graph
Use the books-read data to draw your own line graph on the worksheet. The axes are already drawn for you!
- 📍 Plot a dot for each week's value
- 📏 Connect the dots with a ruler
- 🏷️ Add a title and label both axes
- 🔍 Circle the highest point and lowest point
- ➡️ Draw an arrow showing the overall trend direction
⏱ 12 minutes — when you're done, answer the trend questions on the worksheet.
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Lesson 3
Interpolation — Filling in the Gaps
Interpolation means estimating a value that falls between two known data points.
Example: We know January temperature = 32°F and March = 45°F.
What might February's temperature be?
Estimate: ~38–40°F — reasonable, based on the trend between the two points.
- ✅ Interpolation stays within the data range
- ✅ More confident — the pattern is already established
- ✅ Used to fill gaps in data we didn't collect
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Lesson 4
Extrapolation — Predicting the Future
Extrapolation means predicting a value that falls beyond the known data.
Example: Books read per week has an increasing trend (2→7 over 8 weeks).
What might Week 9 or Week 12 look like?
Estimate: ~7–8 books in Week 9 — possible, but less certain.
- ⚠️ Extrapolation goes beyond the known data range
- ⚠️ Less confident — something unexpected could change the trend
- ⚠️ Always state that it's a prediction, not a fact
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🧠
Brain Break — Trend Detector!
Your teacher will say a scenario. Thumbs up = increasing trend, thumbs down = decreasing, thumbs sideways = steady.
"A plant grows 2cm each week." · "A car slows down." · "Room temperature stays at 70°F." · "A savings account earns interest." · "Ice cream melts in the sun."
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Debrief
Trend Questions — Class Discussion
"For the books-read graph — one student said the trend was increasing, another said it was 'up and down.' Who is right? Can they both be right?"
- Both are describing real things — but "increasing" describes the overall trend
- The week-by-week zigzag is real data variation — not the trend
- How would you describe this to someone who hasn't seen the graph?
- Which description is more useful for making decisions?
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Real-World Connections
Line Graphs in the Real World
🌍 Where We See Them
- Weather — temperature over days
- Economy — stock prices over years
- Health — heart rate during exercise
- Sports — team wins per season
- Science — plant growth over weeks
❓ Questions They Answer
- Is this getting better or worse?
- When did the change happen?
- How fast is it changing?
- What might happen next?
- When was the peak / lowest point?
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Vocabulary Review
Words to Know
Line graph
Graph with connected points showing change over time
Trend
The overall direction data is moving — up, down, or steady
Increase / Decrease
Going up / going down over time
Steady
Staying roughly the same over time
Interpolation
Estimating a value between two known data points
Extrapolation
Predicting beyond the known data (less certain)
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Wrap Up
Session 6 Complete!
- ✅ Line graphs show how values change over time
- ✅ Trend = overall direction, not every individual point
- ✅ Trace the line with your finger to feel the trend
- ✅ Interpolation = filling gaps · Extrapolation = predicting beyond
- ✅ Predictions from trends are estimates — they can be wrong
🔮 Coming up — Session 7: What if we want to compare TWO groups at once? Side-by-side bar charts and comparison statements!