2.4 Small Group · Group 1
Second Practice Form · Re-Teach, Homework or Retake · Same Standard, New Problems
Display Data with Box Plots · Box Plot · Procedural Fluency · Real-World Applications
- A box plot is a simple picture that shows how a set of data is spread out, using just five key numbers: the lowest value, the first quartile (Q1), the median (middle), the third quartile (Q3), and the highest value. We'll walk through a worked example, try one together, then you'll try a few with hints right there when you need them.
- My data, in order: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. There are 11 numbers.
- The middle number is the 6th one, 14, so the median = 14.
- The lower half is 4, 6, 8, 10, 12. Its middle is 8, so Q1 = 8.
- The upper half is 15, 18, 22, 24, 28. Its middle is 22, so Q3 = 22.
- The lowest is 4 and the highest is 28. I draw a box from 8 to 22, a line at 14, and whiskers out to 4 and 28.
- Display Data with Box Plots (Representar datos con diagramas de caja) — Show a data set's five-number summary in a box-and-whisker display.
- Box Plot (Diagrama de caja) — A graph that shows how data is spread using five key numbers.
- Median (Mediana) — The middle number when you put them in order.
- Quartile (Cuartil) — Numbers that split the data into four equal parts.
- Interquartile Range (Rango intercuartílico) — The spread of the middle half of the data (Q3 − Q1).
- Data distribution (Distribución de datos) — How the data looks: where it sits and how spread out it is.
- A common mistake in Display Data: Box Plots is treating a quartile as just one data point instead of the median of a half — for the lower half 4, 8, 10, 14, some students pick 10 (the last value) as Q1 instead of finding the median of that half: Q1 = (8 + 10) ÷ 2 = 9. A second common slip is finding IQR by adding the quartiles instead of subtracting, writing IQR = Q3 + Q1 (like 30 + 18 = 48) instead of IQR = Q3 − Q1 (30 − 18 = 12) — always order the data first, then subtract Q1 from Q3 to find the spread of the middle 50%.
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1 MULTIPLE CHOICE
Two box plots show: Team A has IQR = 8, Team B has IQR = 22. What does this tell you?
- ATeam A's middle 50% is more consistent; Team B's is more spread out
- BTeam B is a better team
- CTeam A has a higher median
- DThe IQRs don't tell you about consistency
✏️ Workspace & Solution Steps
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2 MULTIPLE CHOICE
The Hawks' points per quarter are 2, 4, 5, 7, 8, 10, 12. Resting on the scoreboard, what are the minimum, median, and maximum?
- AMinimum 2, median 7, maximum 12
- BMinimum 2, median 5, maximum 12
- CMinimum 0, median 7, maximum 12
- DMinimum 2, median 8, maximum 10
✏️ Workspace & Solution Steps -
3 MULTIPLE CHOICE
The Comets scored 6, 10, 14, 18, 22, 26, 30, 34 across 8 games. After ordering, what are Q1 and Q3?
- AQ1 = 12, Q3 = 28
- BQ1 = 10, Q3 = 30
- CQ1 = 14, Q3 = 26
- DQ1 = 20, Q3 = 34
✏️ Workspace & Solution Steps -
4 MULTIPLE CHOICE
A box plot for the Rockets shows Min = 8, Q1 = 15, Median = 22, Q3 = 30, Max = 38. The middle 50% of their scores falls between which two values?
- ABetween 15 and 30
- BBetween 8 and 38
- CBetween 8 and 22
- DBetween 22 and 38
✏️ Workspace & Solution Steps
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5 ERROR ANALYSIS
The Added-Quartiles IQR Mistake
- 1Box plot values:Bobcats' box plot: Min = 10, Q1 = 18, Median = 24, Q3 = 30, Max = 40
- 2Goal:Find the interquartile range (IQR).
- 3Student's work:IQR = Q3 + Q1 = 30 + 18 = 48
Which step contains the error? Explain the mathematical misconception and write the correct calculation below.
✏️ Corrected Mathematical Work & Explanation -
6 ERROR ANALYSIS
The Quartile-Is-One-Value Mistake
- 1Data (ordered):Eagles' game scores: 4, 8, 10, 14, 18, 22, 26, 30 (8 values)
- 2Median:With 8 values, Median = (14 + 18) ÷ 2 = 16 ✓
- 3Q1:Lower half = 4, 8, 10, 14 → Q1 = 10
- 4Q3:Upper half = 18, 22, 26, 30 → Q3 = (22 + 26) ÷ 2 = 24
Which step contains the error? Explain the mathematical misconception and write the correct calculation below.
✏️ Corrected Mathematical Work & Explanation
Writing Task: Justify why your mathematical solution is accurate and complete.