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Session 3 of 8
Collecting
Data
We have a great question. Now let's go get the data — carefully and consistently.
📊 Data Science for Young Minds · Grade 3
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Today's Plan
What We're Doing Today
- 🔁 Share data questions from Session 2
- 📋 Three ways to collect data
- | | | ̶| Tally marks — the data collector's best friend
- 🎮 Mini-Survey — survey 10 classmates!
- 📏 Counting & measuring carefully
- 🔍 Error Detective — what went wrong?
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Warm-Up
You Wrote a Data Question!
In Session 2, you designed a data question that's fair, specific, and answerable.
"Who wants to share their question?"
2–3 volunteers share. Quick class vote: "Is this a good data question? Thumbs up or down?"
Today — you'll actually USE that question to collect real data from your classmates!
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Lesson 1
Three Ways to Collect Data
🗣️
Survey
Ask people questions. Best for opinions and preferences.
👁️
Observation
Watch and record what you see. Best for behavior and events.
📏
Measurement
Use tools for exact numbers. Best for size, weight, time.
The method you choose depends on your question. Different questions need different collection methods!
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Lesson 1
Which Method Fits?
Match the question to the right collection method:
- ❓ "What is your favorite fruit?" → Survey — ask people
- ❓ "How many cars pass our school in 10 minutes?" → Observation — watch & count
- ❓ "How tall is each student in the class?" → Measurement — use a ruler/tape
- ❓ "How many students bring lunch vs. buy lunch?" → Observation — watch at lunchtime
- ❓ "How long does it take to read one page?" → Measurement — use a timer
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Lesson 2
Tally Marks — Fast Counting
Tally marks let you count quickly while you're busy listening or watching.
|1
| |2
| | |3
| | | |4
||||̶5 ← cross!
||||̶ |6
||||̶ ||||̶10
The 5th mark crosses the group of 4. Groups of 5 make it easy to count at the end — just count groups and add!
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Lesson 2
Survey Rules — Consistency!
The most important word in data collection: CONSISTENT. Same method, every time.
- Ask the question exactly as written — no changing words mid-survey
- Give all the answer choices — don't hint at which one is "right"
- Record with a tally mark immediately — don't trust your memory
- Each person gets asked only once
- Say "thank you" — be a respectful data collector!
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Activity!
Mini-Survey Time 📋
Grab your worksheet, your clipboard, and your pencil. You have 12 minutes to survey 10 classmates.
- Use YOUR data question from Session 2
- Record answers using tally marks
- Follow the 5 survey rules
- Don't ask the same person twice!
Ready? Go collect some data! 🏃
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🧮
Tally Count Challenge!
Your teacher will write some tally marks on the board.
First team to call out the correct count wins!
Remember: count the groups of 5 first, then add the leftovers.
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Lesson 3
Counting & Measuring Carefully
🔢 Careful Counting
- Point to each item as you count
- Move counted items to a separate pile
- Count again if not sure
- Write down as you go — don't rely on memory
📏 Precise Measuring
- Start from zero — not the edge of the ruler
- Always include the unit (cm, inches, seconds)
- Measure twice if the number seems surprising
- Record the number AND the unit together
Without units, "7" means nothing. Is it 7 cm? 7 feet? 7 minutes?
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Lesson 4
When Things Go Wrong
Every data collector makes mistakes. Here are the most common ones — and how to avoid them:
❌ Changing the question mid-survey → Your data isn't comparable anymore
❌ Forgetting to record an answer → You lose data forever
❌ Asking someone twice → That person counts double, distorting results
❌ Forgetting units when measuring → "7" alone is meaningless
✅ Fix all of these by: preparing your recording sheet BEFORE you start, and following your collection rules consistently.
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Error Detective
Spot the Mistake! 🔍
Your teacher will read 3 scenarios. For each one — what went wrong?
- 🕵️ Scenario 1: Mia records some answers as words and some as tally marks.
- 🕵️ Scenario 2: Sam keeps telling respondents "most people say pizza, just so you know."
- 🕵️ Scenario 3: Dev accidentally asks his best friend the same question twice.
📝 Use your worksheet Part 3 — write the error AND how to fix it.
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Reflection
How Did Your Survey Go?
"What was the hardest part of collecting data today?
What would you do differently next time?"
2–3 students share. Common answers:
- People kept giving answers that weren't one of the choices
- I forgot to tally once
- It was hard to ask and write at the same time
- Someone asked me to repeat the question
All of these = real data science challenges. You just experienced what researchers deal with!
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Vocabulary Review
Words to Know
Survey
Asking people questions to collect data
Observation
Watching and recording what you see
Measurement
Using tools to get exact numbers
Tally mark
A line used for fast counting — 5th mark crosses
Consistency
Recording the same way every time
Collection error
A mistake that makes data unreliable
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Wrap Up
Session 3 Complete! 🎉
- ✅ Three collection methods: survey, observation, measurement
- ✅ Tally marks group in 5s for fast, accurate counting
- ✅ Consistency = record the same way every time
- ✅ You collected real data from real people today!
- ✅ Errors happen — knowing them helps you avoid them
🔮 Coming up — Session 4: All that data you collected is messy! Next session we organize it into tables and frequency charts so the patterns can appear.