Lesson 2.4Represent and Describe Data in a Box Plot
Start hereWords, worked example, and sentence starters
Learning target I can make and read a box plot to summarize a data set.
Why This Matters The basketball league wants to compare scoring across teams. Here are the points scored by each player on the Wildcats in their last game: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. The league needs a quick visual that shows the spread, the middle 50%, and any high or low scorers. Time to build a box plot!
Start hereWords for this lesson
Read each word before you begin. Say it out loud.
| Word | What it means | Example |
|---|---|---|
| Box PlotSpanish: Diagrama de caja | A graph that shows how data is spread using five key numbers. | Box with two whiskers |
| MedianSpanish: Mediana | The middle number when you put them in order. | Data: 10, 15, 20, 25, 30 → median is 20 (the 3rd value) |
| QuartileSpanish: Cuartil | Numbers that split the data into four equal parts. | Q1, median, Q3 |
| Interquartile RangeSpanish: Rango intercuartílico | The spread of the middle half of the data (Q3 − Q1). | If Q1 = 12 and Q3 = 20, then IQR = 20 − 12 = 8 — the middle 50% spans 8 units |
| Data distributionSpanish: Distribución de datos | How the data looks: where it sits and how spread out it is. | A box plot where the median is centered in the box shows symmetric distribution |
| VariabilitySpanish: Variabilidad | How spread out the numbers are. | Small IQR = low variability in the middle 50%. Large IQR = high variability |
How it worksWorked example
These numbers are not on your problems. The steps are. Follow them with your own numbers.
Times (min): 14, 5, 20, 9, 23, 11, 16.
- Order: 5, 9, 11, 14, 16, 20, 23. Median = 14.
- Lower half 5, 9, 11: Q1 = 9. Upper half 16, 20, 23: Q3 = 20.
- Box from 9 to 20, line at 14, whiskers to 5 and 23.
Answer: 5, 9, 14, 20, 23
Now you trySame steps, your turn
The steps are the same as the worked example. The numbers are yours. Do the work.
New, smaller data set: 2, 5, 5, 8, 11. First, what is the median (the middle value)?
Say it and write itSentence starters
Finish each sentence out loud with a partner. Then use them in your writing.
- In order the values are .
- The median is , so the lower half is .
- Quartile 1 is and quartile 3 is .
- The box stretches from to , which holds of the data.
Word bank box plotquartilemedianminimummaximumwhiskerboxorderlower halfupper halfmiddlespread
Watch out!A common mistake
A common mistake in Display Data: Box Plots is treating a quartile as just one data point instead of the median of a half
Lesson 2.4Represent and Describe Data in a Box Plot
Version ASupported practice
Learning target I can make and read a box plot to summarize a data set.
Why This Matters The basketball league wants to compare scoring across teams. Here are the points scored by each player on the Wildcats in their last game: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. The league needs a quick visual that shows the spread, the middle 50%, and any high or low scorers. Time to build a box plot!
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1Circle the letter of the best answer. Show how you know.
On a box plot, what does the line inside the box represent?
- AThe median
- BThe mean
- CThe mode
- DThe range
Hint Picture a box plot: a box with whiskers, and a line cutting through the box. That line marks the CENTER of the data.
Show your work -
2Write the name of the correct group on each line.
Order the steps for making a box plot.
- Step 1: Order the data from least to greatest
- Step 2: Find the median (middle value)
- Step 3: Find Q1 (median of the lower half)
- Step 4: Find Q3 (median of the upper half)
- Step 5: Draw the box from Q1 to Q3 with a line at the median, and whiskers to min and max
Hint Always order the data first before finding any measures.
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3Circle the letter of the best answer. Show how you know.
A box plot shows: Min = 10, Q1 = 15, Median = 20, Q3 = 28, Max = 35. What is the interquartile range (IQR)?
- A10
- B13
- C20
- D25
Hint You're given five numbers, but IQR only uses two of them: Q1 and Q3. Ignore the min, median, and max.
Put the data in orderWork- 1OrderSmallest to largest.
- 2CountHow many values?
- 3LocateMiddle, or add and divide.
- 4AnswerSay which measure it is.
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4Circle the letter of the best answer. Show how you know.
What percentage of data falls between Q1 and Q3 on a box plot?
- A25%
- B50%
- C75%
- D100%
Hint Quartiles cut the data into 4 equal parts — 'quart' like 'quarter.' Each part holds the same share of the data.
Put the data in orderWork- 1OrderSmallest to largest.
- 2CountHow many values?
- 3LocateMiddle, or add and divide.
- 4AnswerSay which measure it is.
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5Circle the letter of the best answer. Show how you know.
Find the range of: 14, 22, 8, 31, 17
- A8
- B39
- C23
- D31
Hint Range = how far the data stretches: the gap between the biggest and smallest values only. The middle values don't matter.
Put the data in orderWork- 1OrderSmallest to largest.
- 2CountHow many values?
- 3LocateMiddle, or add and divide.
- 4AnswerSay which measure it is.
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6Find the mistake. Explain it, then show the correct work.
The Added-Quartiles IQR Mistake
- 1Box plot valuesBobcats' box plot: Min = 10, Q1 = 18, Median = 24, Q3 = 30, Max = 40
- 2GoalFind the interquartile range (IQR).
- 3Student's workIQR = Q3 + Q1 = 30 + 18 = 48
Which step has the mistake? Explain what went wrong, then show the correct work.
Hint IQR stands for InterQuartile RANGE — a range is found by subtracting, not adding.
Correct workCorrect answer:
Explain your thinkingThe IQR is Q3 − Q1 = 26 − 10 = 16. What does this tell you about the middle 50% of scorers?
Sentence starter The middle 50% of players scored between ___ and ___ points. The IQR of ___ means the middle half of the data is spread across ___ points. This tells me ___.
Lesson 2.4Represent and Describe Data in a Box Plot
Version BCore practice
Learning target I can make and read a box plot to summarize a data set.
Why This Matters The basketball league wants to compare scoring across teams. Here are the points scored by each player on the Wildcats in their last game: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. The league needs a quick visual that shows the spread, the middle 50%, and any high or low scorers. Time to build a box plot!
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1Complete the table. Show how you found each value.
Complete the table.
Measure Value Data: 5, 8, 12, 15, 18, 20, 25, 30, 35 Minimum Q1 (median of lower half: 5, 8, 12, 15) Median Q3 (median of upper half: 20, 25, 30, 35) Maximum IQR (Q3 − Q1) Show your work -
2Write the letter of the matching item on each line.
Match each box plot term to its meaning.
- Minimum
- Q1
- Median
- Q3
- IQR
- Maximum
- ASmallest value in the data set
- BMedian of the lower half
- CMiddle value of the entire data set
- DMedian of the upper half
- EQ3 − Q1 (spread of middle 50%)
- FLargest value in the data set
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3Mark and label each value on the number line.
Data: 3, 5, 7, 9, 11, 13, 15. Place the five-number summary on the number line.
Show your thinking -
4Circle the letter of the best answer. Show how you know.
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
Show your work
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5Find the mistake. Explain it, then show the correct work.
The Quartile-Is-One-Value Mistake
- 1Data (ordered)Eagles' game scores: 4, 8, 10, 14, 18, 22, 26, 30 (8 values)
- 2MedianWith 8 values, Median = (14 + 18) ÷ 2 = 16 ✓
- 3Q1Lower half = 4, 8, 10, 14 → Q1 = 10
- 4Q3Upper half = 18, 22, 26, 30 → Q3 = (22 + 26) ÷ 2 = 24
Which step has the mistake? Explain what went wrong, then show the correct work.
Correct workCorrect answer:
Explain your thinkingThe IQR is Q3 − Q1 = 26 − 10 = 16. What does this tell you about the middle 50% of scorers?
Lesson 2.4Represent and Describe Data in a Box Plot
ChallengeExtension
Learning target I can make and read a box plot to summarize a data set.
Why This Matters The basketball league wants to compare scoring across teams. Here are the points scored by each player on the Wildcats in their last game: 4, 6, 8, 10, 12, 14, 15, 18, 22, 24, 28. The league needs a quick visual that shows the spread, the middle 50%, and any high or low scorers. Time to build a box plot!
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1Write the letter of the matching item on each line.
Match each box plot feature with what it tells you about the data.
- Long right whisker, short left whisker
- Median line centered in the box
- Very small box (small IQR)
- Very large box (large IQR)
- ASkewed right — some high values stretch far from the box
- BApproximately symmetric in the middle 50%
- CMiddle 50% is tightly clustered — consistent
- DMiddle 50% is widely spread — high variability
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2Find the mistake. Explain it, then show the correct work.
Find the Box Plot Error
- 1Data3, 7, 9, 12, 15, 18, 21
- 2Min and MaxMin = 3, Max = 21
- 3MedianMiddle value = 12 ✓
- 4Q1 and Q3Q1 = 9, Q3 = 18
Which step has the mistake? Explain what went wrong, then show the correct work.
Correct workCorrect answer: -
3Answer in complete sentences.
Two basketball teams played 9 games each. Team A: 40, 42, 44, 46, 48, 50, 52, 54, 56. Team B: 30, 35, 40, 45, 48, 50, 55, 60, 65. Find the five-number summary and IQR for each team. Which team is more consistent? Which has a wider spread in the middle 50%?
Write your answer