Concept 7 of 9
The Data Stamper: Line Plots
Today's big idea
Stacking repeats into towers turns a plain list of numbers into a picture.
Heights 5, 6, 6, 7, 7, 7, 8 stack up, and the tallest tower sits at 7.
How it works
👀 What's going on?
You measured ten plants in the school garden. Written out as a sentence, that is a chore to read. Stacked into a picture, it takes a couple of seconds to understand.
💡 Here's the trick
Look at the plot above. The heights 5, 6, 6, 7, 7, 7 and 8 turn into towers of X marks above a number line. The tower at 7 is the tallest with three marks, so 7 cm is the most common height. Repeats stack up, so the shape of the plot tells you the story.
🪄 How to do it
- 1.Draw a number line covering every value, as the picture above runs from 5 to 8.
- 2.Stamp one X above the right number for each measurement you took.
- 3.Let the repeats stack into towers, then read the towers.
✍️ Try it
Using that plot, how many plants are taller than 6 cm? And how many plants were measured altogether?
Taller than 6 cm means the 7 tower and the 8 tower, so 3 + 1 = 4 plants. The total is every X added up, 1 + 2 + 3 + 1 = 7 plants. Counting towers answers both without going back to the original list.
⚠️ Watch out
You might be thinking 'taller than 6' should include the plants that measure exactly 6 cm. It does not. Taller than means strictly above, so those two stay out. Had it said 6 cm or more, they would both count.
🌟 Why this matters
Sports scores, rainfall records and class survey results all get shown this way. A picture of the data answers questions far faster than a list does.
Exam tip: Read the wording for more than against at least, because that one word changes the count.
Watch me solve one
Quanta solves it
“Watch how I think through one of these — then you try.”
THE PROBLEM
“Scores: 3, 4, 4, 5, 5, 5, 8. What's most common?”
- 1
Draw a number line
Stretches from 3 up to 8 — the range of scores.
- 2
Stamp an X for every value
3 → 1 X. 4 → 2 Xs. 5 → 3 Xs. 8 → 1 X.
- 3
Find the tallest stack
The stack above 5 is the tallest — three X's.
- 4
Most common ✓
Most common score = 5
Now you try one — same steps, different story 👇
See it in action
⚡ Time to play!
Stamp each flight distance onto the line plot one at a time!
Next distance: 2m
Quick check
✅ VERIFICATION
A line plot has 2 X above 3, 4 X above 4 and 1 X above 5. How many items were measured?
⚡ Finish the activity above first to answer.
Keep going!
Up next: The Unitary Method
Find 1 unit, then multiply to get any amount.