Math lesson plan · 7th grade (Year 8 in England) · 45 minutes
Compare two groups using centre and spread
Statistics and probability
CCSS 7.SP.B.3CCSS 7.SP.B.4England: KS3 StatisticsEngland: GCSE Foundation Statistics
Objective and success criteria
Students will: Compare two groups using centre and spread.
- 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: Mean absolute deviation (MAD); Find quartiles and the interquartile range
Leads to: the next skill in this area.
Materials: Squared paper for charts, Class survey data, Sticky notes for a live chart, Mini whiteboards and pens, Printed student sheet (below).
Warm-up · 5 min
- Quick retrieval from earlier learning (Mean absolute deviation (MAD); Find quartiles and the interquartile range). Students answer on mini whiteboards.
- Show answers together and note who needs support in the main task.
- The mean of 15, 11, 13, 25 is 16. Find the mean absolute deviation. → 4.5Prompt: Find how far each value is from the mean (ignore signs).
- Find the upper quartile (Q3) of: 41, 25, 15, 21, 7, 35, 35 → 35Prompt: Order the data and find the median.
- Daniel's scores: 18, 20, 22, 20. Hiro's scores: 14, 26, 20, 20. Both have mean 20. Whose scores are more consistent (smaller MAD)? (Daniel / Hiro) → DanielPrompt: MAD measures how spread out the data is around the mean.
Hook · 5 min
- Take a quick class survey (favorite fruit, travel to school) and ask what the results tell us.
- Share the objective: Compare two groups using centre and spread. Read the success criteria together.
I do: model it · 10 min
- Work through the example out loud, saying why you do each step, not just what you do.
- Example: Class A's mean height is 145 cm and Class B's is 157 cm. Both have a mean absolute deviation of 3 cm. The difference in means is how many MADs?
- Step 1: 157 − 145 = 12
- Step 2: 12 ÷ 3 = 4
- Answer: 4
- Pause after each step and ask a student to say what comes next.
We do: guided practice · 10 min
- Do these together. Students try each step on whiteboards before you reveal it.
- Use the hints as prompts rather than giving the answer.
- Class A's mean height is 148 cm and Class B's is 158 cm. Both have a mean absolute deviation of 5 cm. The difference in means is how many MADs? → 2Prompt: Find the difference between the means.
- Minutes of daily reading. Nia's group: 14, 14, 16, 13, 19, 25, 27. Ethan's group: 25, 24, 24, 24, 31, 33, 37. Using medians, which group typically reads for longer? (Nia's group / Ethan's group / They are the same) → Ethan's groupPrompt: Order each list and find the middle value.
You do: independent practice · 10 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 8 questions are on the student sheet below, with answers in the key.
Exit ticket · 5 min
- Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.
- Two basketball players' points per game: Ravi has median 18 and IQR 8; Aisha has median 18 and IQR 5. Who is more consistent? (Ravi / Aisha) → AishaPrompt: Consistency is about spread, not the average.
- Minutes of daily reading. Grace's group: 24, 22, 28, 30, 27, 21, 30. Tariq's group: 33, 29, 35, 37, 36, 29, 39. Using medians, which group typically reads for longer? (Grace's group / Tariq's group / They are the same) → Tariq's groupPrompt: Order each list and find the middle value.
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: Mean absolute deviation (MAD).
- 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
- 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-7.
Free lesson plan from eurekami.com/lesson-plan-builder