Stem-and-leaf plot

A graph for displaying the distribution of a numerical variable that is similar to a histogram but retains some information about individual values.

Ideally the numbers in the ‘stem’ represent the highest place-value digit in the values and the ‘leaves’ display the second highest place-value digits in each individual value.

To compare the distribution of a numerical variable for two categories of a category variable, a back-to-back stem-and-leaf plot can be drawn, in which the stem is placed at the centre and the leaves for the values of the numerical variable for one category are drawn on one side of the stem and the leaves for the other category are drawn on the other side.

Stem-and-leaf plots are particularly useful when the number of values to be plotted is not large.

Example 1

The actual weights of a random sample of 50 male university students enrolled in an introductory Statistics course at the University of Auckland are displayed on the stem-and-leaf plot below.

Actual weights of male university students (kg)

The stem unit is 10kg.

Example 2 (Back-to-back stem-and-leaf plot)

The actual weights of random samples of 50 female and 50 male university students enrolled in an introductory Statistics course at the University of Auckland are displayed on the back-to-back stem-and-leaf plot below.

Actual weights of university students (kg)

The stem unit is 10kg.

Alternative: stem plot

Curriculum achievement objectives references

Statistical investigation: Levels 4, 5, 6, 7, 8.

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