Question

When and how do we split stems for a stem and leaf plot?

Answer 1

A stem-leaf plot can be informative about some meaningful characteristics
of the data. To obtain such a plot, we first arrange the observations in ascending
order. The leaf is the last digit in a number. The stem contains all other digits (When
the data consists of very large numbers, rounded values to a particular place, like
hundred or thousand, are used a stem and leaves). In the leaf plot, there are two
columns, first representing the stem, separated by a line from the second column
representing the leaves. Each stem is listed only once and the leaves are entered in
a row. The plot helps to understand the relative density of the observations as well
as the shape. The mode is easily displayed along with the potential outliers. Finally,
the descriptive statistics can be easily worked out from the diagram.

Example 1.14. We illustrate the stem-leaf plot for a small data set: 36, 57, 52, 44,
47, 51, 46, 63, 59, 68, 66, 68, 72, 73, 75, 81, 84, 106, 76, 88, 91, 41, 84, 68, 34,
38, 54.

In most applications of statistics, stem and leaf plots have few advantages over stacked dot plots. Even though they contain more detail about the values, this extra information rarely helps you to understand the data.

However for assessment data, stem and leaf plots are a good way to present marks to students since they can both easily see the overall distribution and count exactly their own position in the class.