Stem and leaf diagrams

A stem and leaf diagram is one way of grouping data into classes and showing the shape of the data.


A maths test is marked out of {50}. The marks for the class are shown below:

Table showing the marks from a maths test for 30 pupils within a class

This is all the information that you require, but it is difficult to interpret. For example, is it easy to tell whether more children got marks in the {20}s than the {30}s? Can you tell at a glance what the highest mark was, or whether more than one person achieved the same result?

One way to represent the data so that you can answer these questions at a glance is in a stem and leaf diagram. This diagram shows the same results as the example above:

Stem and leaf diagram
  • The stem and leaf diagram is formed by splitting the numbers into two parts - in this case, tens and units.
  • The tens form the 'stem' and the units form the 'leaves'.
  • This information is given in the key.

The numbers are usually ordered, so the row:

Stem and leaf row diagram

shows the numbers {21}, {23}, {24}, {24}, {25} and {27} in order.


Using the stem and leaf diagram above, answer the following questions.

Q1. How many children scored {36}?

Q2. What was the most common score?

A1. You can work this out by looking at the {3} column in the tens:

Stem and leaf diagram

Therefore {2} children score {36}.

A2. You can work this out from the stem and leaf diagram below:

Stem and leaf diagram

Therefore {17} is the most common score.

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