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Session 7: Comparing Two Groups

Grade 4 Data Science ยท Instructor Cheatsheet ยท Side-by-Side Bar Charts & Comparison Writing

โฑ 60 min ๐Ÿ‘ฅ Pairs + Whole Group ๐Ÿ“Š Double Bar Charts โœ๏ธ Comparison Sentences
Session Agenda
TimePhaseActivityNotes
0โ€“7 minHookSame question, two different classrooms โ€” who reads more?Show two tallies side by side on board
7โ€“18 minTeachDouble bar chart anatomy โ€” two bars per category, legendColor-code Group A blue, Group B teal on board
18โ€“32 minActivity 1Pairs build a double bar chart from pet preference dataPre-draw axes; students add bars with colored pencils
32โ€“42 minTeachComparison sentence frames: "more," "less," "both," "while"Model 3 complete sentences from the chart
42โ€“52 minActivity 2Write 3 comparison statements from their chartSentence starters on board, circulate
52โ€“57 minBrain BreakStand if your answer is higher for Group A; sit for Group BCall out data questions rapidly
57โ€“60 minCloseGallery share + preview Session 8 capstonePreview data story project
Activity Data โ€” Pet Preferences (Two Classrooms)
Reference Data Set โ€” Write on Board
Pet ๐Ÿ”ต Class A (Blue) ๐Ÿฉต Class B (Teal)
Dog128
Cat711
Fish46
Bird35
Other24

Total surveyed: Class A = 28 students ยท Class B = 34 students. When comparing, emphasize the raw counts AND note the class size difference as a discussion point.

Teaching Double Bar Charts
Anatomy of a Double Bar Chart
  • X-axis: categories (pet type)
  • Y-axis: count/frequency
  • Each category has two bars side by side
  • Legend identifies which color = which group
  • Bars in same category must touch or be close
  • Leave space between different categories
Class A Class B
Common Student Mistakes
  • Drawing bars for different categories on top of each other โ€” remind: side by side, same category
  • Forgetting the legend โ€” always add it
  • Inconsistent bar widths โ€” use a ruler
  • Starting Y-axis at a non-zero value โ€” always start at 0
  • Mixing up which color is which group
Comparison Sentence Frames โ€” Model These on Board
Sentence Frames for Comparison Writing
Class A preferred dogs more than Class B โ€” 12 students vs. 8 students.
Class B preferred cats more than Class A, with 11 vs. 7 students.
Both classes had dogs as their top choice, but by different amounts.
Class A had the most dog fans, while Class B had the most cat fans.
The difference between classes for dogs was 12 โˆ’ 8 = 4 students.

Post these frames on the board during Activity 2. Students choose any frame that fits the comparison they want to make.

Discussion Questions & Sample Answers
Reading the Chart
  • Q: Which pet did Class A like most?
    A: Dog (12 students)
  • Q: Which pet did Class B like most?
    A: Cat (11 students)
  • Q: For which pet were the two classes closest in number?
    A: Bird (3 vs. 5, diff = 2)
  • Q: For which pet was the difference largest?
    A: Dog (12 vs. 8, diff = 4)
Deeper Thinking
  • Q: Class B has more total students. Does that make comparing fair?
    A: Guide: we could use fractions/percentages โ€” introduce as stretch
  • Q: Can you think of a reason why two classrooms might have different pet preferences?
    A: Open-ended: neighborhood, allergies, family backgrounds
  • Q: Which comparison sentence tells the most interesting story?
    A: Discussion โ€” no single right answer

Answer Key โ€” Worksheet Questions

๐Ÿง  Neurodiversity & Inclusion Tips

Supplies
๐Ÿ“ Rulers โœ๏ธ Pencils ๐Ÿ”ต Blue pencils/crayons ๐Ÿฉต Teal/light-blue pencils ๐Ÿ“‹ Worksheets ๐Ÿ–Š๏ธ Whiteboard markers (2 colors) ๐Ÿ“Š Graph paper (backup)