Stem-and-Leaf Diagrams
A stem-and-leaf diagram splits each value into a leading part, the stem, and a final digit, the leaf. Unlike a grouped table, it keeps every original value.
Back-to-back stem-and-leaf
LinnetsstemPuffins845 99 7 4 151 5 5 8 98 5 4 4 062 4 4074
Key: 4 | 5 | 5 means 54 s for Linnets and 55 s for Puffins.
Build a single diagram
- Choose the place value. Decide what the stem and leaf mean. For 53 marks, the stem could be 5 tens and the leaf 3 units.
- Write every stem in the range. Keep an empty stem if no value belongs there. Equal stem intervals make gaps in the data visible.
- Add and order one leaf per value. On a right-hand diagram, leaves increase away from the stem. Repeated values need repeated leaves.
- Add a complete key and count. A key such as fixes the place value and unit. The number of leaves must equal the data count.
Worked example
Keep every value
The data are .
1 | 2 4 7
2 | 1 1 3
3 | 5
Key: represents 12. Seven leaves confirm that no value was lost.
Put two groups on one shared stem
- The shared stem forces both groups onto the same scale, making their distributions easy to compare.
- On both sides, the smallest leaf is nearest the stem. Left-hand leaves therefore appear in decreasing order as you read left to right.
- Label both groups. The key must decode one value on each side and include the unit.
Common mistake
Do not draw two separate diagrams or use commas between leaves. The shared stem, ordering, labels and key are all part of the construction.
Now you try
Your turn9709/53 Oct/Nov 2025 Q6(a) [4 marks]
Construct a back-to-back stem-and-leaf diagram for these cycling times, in minutes.
Linnets: 48, 51, 54, 57, 59, 60, 64, 64, 65, 68, 70.
Puffins: 45, 49, 51, 55, 55, 58, 59, 62, 64, 64, 74.
Show worked answer
845 99 7 4 151 5 5 8 98 5 4 4 062 4 4074
Key: means 54 minutes for Linnets and 55 minutes for Puffins.