What is a Stem-and-Leaf Diagram?
A stem-and-leaf diagram (also called a stem-and-leaf plot or stemplot) is a way of organising numerical data so you can see every single value while also getting a picture of how the data is distributed.
A method of displaying numerical data where each value is split into a stem (the leading digit or digits) and a leaf (the last digit). The stems are listed in a column, and the leaves are written in order next to their corresponding stem.
Think of it as a hybrid — it's part table, part chart. Unlike a bar chart where you lose the individual values, a stem-and-leaf diagram keeps every piece of data visible while still showing you the shape of the distribution.
Imagine sorting a pile of coins into rows by their value (5c, 10c, 20c, 50c). Each row is a "stem," and the individual coins sitting in that row are the "leaves." You can count exactly how many coins you have AND see which row has the most — all at once.
In MYP Sciences, you'll use stem-and-leaf diagrams to organise data from experiments — for example, recording the heights of plants grown under different light conditions, or comparing reaction times between two groups of students.
How Stems and Leaves Work
To build a stem-and-leaf diagram, you split each data value into two parts:
- The stem = all the digits except the last one
- The leaf = the last digit only
For example, with the number 47:
- Stem = 4
- Leaf = 7
For the number 123:
- Stem = 12
- Leaf = 3
For a single-digit number like 6:
- Stem = 0
- Leaf = 6
Each leaf must be a single digit (0–9). If you find yourself writing two digits as a leaf, you've split the number incorrectly. Go back and check!
Always include a key with your stem-and-leaf diagram. For example: Key: 4 | 7 = 47. Without a key, the reader won't know what the stems and leaves represent.
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