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 10, 5, 10, 5, 5 is 7. Find the mean absolute deviation. → 2.4Prompt: Find how far each value is from the mean (ignore signs).
- Find the upper quartile (Q3) of: 39, 34, 9, 17, 2, 40, 48 → 40Prompt: Order the data and find the median.
- Ava's scores: 24, 25, 26, 25. Omar's scores: 22, 28, 25, 25. Both have mean 25. Whose scores are more consistent (smaller MAD)? (Ava / Omar) → AvaPrompt: 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 140 cm and Class B's is 155 cm. Both have a mean absolute deviation of 5 cm. The difference in means is how many MADs? → 3Prompt: Find the difference between the means.
- Minutes of daily reading. Kofi's group: 24, 25, 30, 12, 29, 19, 10. Sam's group: 32, 35, 41, 23, 41, 30, 21. Using medians, which group typically reads for longer? (Kofi's group / Sam's group / They are the same) → Sam'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.
- Class A's mean height is 143 cm and Class B's is 159 cm. Both have a mean absolute deviation of 4 cm. The difference in means is how many MADs? → 4Prompt: Find the difference between the means.
- Two basketball players' points per game: Felix has median 18 and IQR 9; Kofi has median 18 and IQR 11. Who is more consistent? (Felix / Kofi) → FelixPrompt: Consistency is about spread, not the average.
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