Take two or three hands-up answers, not open call-outs. Do not settle the question yet — the point is to plant doubt about whether one number (the mean) tells the whole story. Give five seconds of quiet think-time before any hands go up.

Point at the two dot plots in turn. Both share a mean of 15, so the mean line lands in the same spot on both. Ask the class to look instead at how stretched out each set is. Revoice a strong answer: so the middle is the same, but one class is all bunched up and the other is scattered. Hold the word spread until a pupil offers it, then name it. Do not narrate the second dot plot before pupils have looked — let them spot the difference.

Walk the class through the six snapshots in order; take the mean and range aloud from each plot before asking for the comparison sentence. This is a teacher-led look at the board, not pupil board turns.

• First comparison (plots 1 and 2): identical means of 15 hide very different spreads — range 2 against range 20.
• Second comparison (plots 3 and 4): Set A has the higher mean (16) yet the lower top score (17), while Set B has a lower mean (14) but reaches 21. A bigger mean does not always mean bigger values throughout.
• Outlier comparison (plots 5 and 6): ask which number is doing all the stretching? and revoice: so one score can pull the range wide open while the middle barely shifts.

This is the practice round — pupils take turns at the board, check each answer, and the class confirms before moving on. Keep the board work brisk rather than over-explaining.

Collect a quick raw data set from the class first (a show of hands or a fast round-the-room count), then split it into two sensible groups. As pupils take turns entering each group and reading the overlay, insist every claim carries a number: Group 1 is more consistent because its range is 6 and Group 2's range is 18. For the stretch, revoice: a lower mean but a smaller spread means every value is closer to typical — sometimes that is exactly what you want.

If the live data does not throw up a lower-mean/smaller-spread group, use this prepared pair: Group 1 = 11, 12, 12, 13 (mean 12, range 2) and Group 2 = 8, 12, 16, 20 (mean 14, range 12). Group 1 has the lower mean but is far more consistent, so it can be argued the better one.