Math lesson plan · 6th grade (Year 7 in England) · 30 minutes
Find quartiles and the interquartile range
Statistics and probability
CCSS 6.SP.B.5.CEngland: KS3 StatisticsEngland: GCSE Foundation Statistics
Objective and success criteria
Students will: Find quartiles and the interquartile range.
- I can answer questions on today's skill on my own, without help.
- I can explain each step and say why it works.
- I can check my answer and spot a mistake.
Before and after
Needs first: Find the median of an even-sized data set
Leads to: Compare two groups using centre and spread
Materials: Squared paper for charts, Class survey data, Sticky notes for a live chart, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 4 min
- Quick retrieval from earlier learning (Find the median of an even-sized data set). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- Find the median: 5, 28, 39, 15, 10, 38, 30, 20 → 24Prompt: Put the values in order first.
- Ten students recorded minutes of screen time: 103, 160, 48, 50, 169, 102, 139, 156, 37, 49. What is the median? → 102.5Prompt: Order the 10 values.
- Find the median: 24, 15, 23, 3, 19, 18 → 18.5Prompt: Put the values in order first.
Hook · 3 min
- Take a quick class survey (favorite fruit, travel to school) and ask what the results tell us.
- Share the objective: Find quartiles and the interquartile range. Read the success criteria together.
I do: model it · 7 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Find the lower quartile (Q1) of: 20, 48, 33, 36, 8, 14, 32, 2, 45, 2, 39
- Step 1: 2, 2, 8, 14, 20, 32, 33, 36, 39, 45, 48
- Step 2: Median = 32
- Step 3: Q1 = 8
- Answer: 8
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 6 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Find the lower quartile (Q1) of: 35, 39, 25, 20, 13, 22, 32, 4, 24, 15, 20 → 15Prompt: Order the data and find the median.
- Find the interquartile range (IQR) of: 49, 22, 43, 38, 12, 35, 57, 53 → 22.5Prompt: Order the data. Split it into a lower half and an upper half.
You do: independent practice · 7 min
- Students work on the student sheet. Circulate and check the first two answers of every student early.
- Students who finish: write a question of their own for a partner, with the answer.
The 6 questions are on the student sheet below, with answers in the key.
Exit ticket · 3 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Find the interquartile range (IQR) of: 59, 59, 11, 58, 40, 53, 46, 52, 23, 15 → 35Prompt: Order the data. Split it into a lower half and an upper half.
- A box plot of reaction times (hundredths of a second) shows: minimum 12, Q1 22, median 25, Q3 32, maximum 38. What is the range? → 26Prompt: The box goes from Q1 to Q3; the whiskers go to the minimum and maximum.
Watch out for
- Forgetting to put data in order before finding the median.
- Reading a bar's height wrongly when the scale goes up in 2s or 5s.
Support and stretch
Support
- Review first: Find the median of an even-sized data set.
- Use concrete materials: squared paper for charts.
- Give the first step of each question, or a partly worked example to finish.
- Pair with a confident partner for the guided practice.
Stretch
- Move on to: Compare two groups using centre and spread.
- Explain a common mistake in writing and how to fix it.
- Write a word problem that uses today's skill, then solve a partner's.
Homework and more practice
Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-6.
Free lesson plan from eurekami.com/lesson-plan-builder