📋 Teacher Cheat Sheet — Session 4: Organizing Numerical Data

Data Science for Young Minds · Grade 4 · Ages 9–10

~60 min Ages 9–10 Session 4 of 8 ND-Friendly

⏱ Session Agenda

Time	Block	What's Happening
0–5	🎯 Hook	Give each student a sticky dot. Number line on board (0–200 by 10s). Students place their dot at their own reading score. Watch the line plot form.
5–18	📖 Lesson	Line plots (dot plots) — reading and building · Cluster, spread, range, min, max
18–30	🎮 Activity 1	Build a class line plot from a data set of 20 quiz scores (worksheet)
30–45	📖 Lesson 2	Stem-and-leaf plots — how to build one, how to read one
45–55	🎮 Activity 2	Pair work: build a stem-and-leaf from same 20 scores; compare to line plot
55–60	👋 Close	"What can a stem-and-leaf show that a line plot can't? And vice versa?"

Pacing note: The physical dot sticker hook is worth the 5 minutes — students immediately understand what a line plot IS because they built one with their bodies. Don't skip it.

📦 Materials Needed

Sticky dot stickers (1 per student) Masking tape number line on board or floor Worksheets (with line plot grid and stem-and-leaf template) Pencils and rulers Colored pencils (optional for highlighting clusters)

💡 Data set to use: 20 quiz scores: 72, 85, 91, 68, 74, 85, 90, 63, 77, 85, 92, 74, 88, 65, 71, 80, 85, 77, 93, 68

📚 Key Vocabulary

Line plot / dot plot — a number line with X marks or dots showing frequency

Stem-and-leaf plot — organizes data using tens (stems) and ones (leaves)

Range — the difference between the maximum and minimum values

Cluster — a group of data points that are close together

Spread — how far apart the data values are from each other

Minimum / Maximum — smallest / largest value in the data set

💬 Discussion Questions + Teacher Notes

"Where do most of the scores cluster? What does that tell us?"
→ The cluster (80s) shows where most students scored. This is visual interpretation — students are reading the line plot before they can define "mode" or "average." Let them use natural language first.
"What's the range of the scores? What does a large vs. small range mean?"
→ Range = max − min = 93 − 63 = 30. A large range means scores varied widely — some students understood the material much better than others. A small range would mean everyone scored similarly.
"Are there any gaps in the data? What might a gap mean?"
→ A gap (e.g., no scores in the 50s) can indicate something real: no students failed catastrophically. Gaps are as informative as clusters.
"What can you see in the stem-and-leaf that's harder to see in the line plot?"
→ The exact values! A line plot shows frequency but rounds to the nearest unit. Stem-and-leaf preserves the exact numbers while still showing distribution.
"What could you do with this data that you couldn't do just from looking at the raw list?"
→ See patterns instantly, find min/max quickly, identify where most data sits, spot outliers visually. This is the whole point of organizing data — it enables interpretation.

🎮 Stem-and-Leaf Construction Guide

Data: 72, 85, 91, 68, 74, 85, 90, 63, 77, 85, 92, 74, 88, 65, 71, 80, 85, 77, 93, 68

Steps to build:

Order all values from smallest to largest first
Write the stems (tens digits) in a column: 6, 7, 8, 9
For each value, write the leaf (ones digit) next to its stem
Order leaves on each row from smallest to largest

Stem | Leaves
6 | 3 5 8 8
7 | 1 2 4 4 7 7
8 | 0 5 5 5 5 8
9 | 0 1 2 3
Key: 7|2 = 72

What to point out: The 80s row has 6 leaves — that's the cluster. Range = 93 − 63 = 30. Mode = 85 (appears 4 times).

🎯 Opening Hook

Tape a number line on the board (60–100 by 5s). Give each student a sticky dot. Call out today's data set scores one at a time — students place a dot when they hear their assigned score.

→ The class watches the line plot build in real time. Then ask: "What do you notice about where most dots landed?"

📊 Line Plot vs. Stem-and-Leaf

Line Plot (Dot Plot):
→ Shows frequency visually
→ Easy to see clusters and gaps
→ Best for smaller data sets
→ Loses exact values if rounded

Stem-and-Leaf:
→ Preserves exact values
→ Shows distribution by tens
→ Easy to find median and mode
→ Works well for 2-digit numbers

🧠 ND-Friendly Tips

Physical first — Sticky dots on the number line before any definitions. Tactile + visual = faster understanding.
Pair work for stem-and-leaf — One partner calls out values, the other writes. This externalizes the cognitive load of tracking two digits simultaneously.
Color-code the cluster — Have students circle or highlight where most leaves appear. Visual emphasis on the key finding.
Provide pre-drawn axes — For students who struggle with spacing/layout, give a printed template with stems already written.
Order first, always — Remind students to sort all 20 values before starting the stem-and-leaf. This prevents errors and builds number sense.