• 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.

1. The mean of 12, 16, 15, 1 is 11. Find the mean absolute deviation. → 5Prompt: Find how far each value is from the mean (ignore signs).
2. Find the upper quartile (Q3) of: 6, 20, 30, 43, 25, 37, 20 → 37Prompt: Order the data and find the median.
3. Felix's scores: 19, 20, 21, 20. Liam's scores: 15, 25, 20, 20. Both have mean 20. Whose scores are more consistent (smaller MAD)? (Felix / Liam) → FelixPrompt: MAD measures how spread out the data is around the mean.

• 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.

• 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.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Class A's mean height is 152 cm and Class B's is 164 cm. Both have a mean absolute deviation of 4 cm. The difference in means is how many MADs? → 3Prompt: Find the difference between the means.
2. Minutes of daily reading. Daniel's group: 19, 22, 10, 27, 23, 23, 11. Aisha's group: 23, 25, 15, 31, 25, 28, 16. Using medians, which group typically reads for longer? (Daniel's group / Aisha's group / They are the same) → Aisha's groupPrompt: Order each list and find the middle value.

• 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.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. Class A's mean height is 159 cm and Class B's is 174 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.
2. Minutes of daily reading. Sofia's group: 24, 17, 13, 19, 10, 25, 27. Sam's group: 28, 22, 19, 26, 14, 33, 33. Using medians, which group typically reads for longer? (Sofia's group / Sam's group / They are the same) → Sam's groupPrompt: Order each list and find the middle value.

Free online practice with hints and printable worksheets for this skill: eurekami.com/math/grade-7.