ANATOMY OF A STEM-AND-LEAF PLOT
Stem-and-Leaf Plots are a simple way to present quantitative data. For small data sets this plot presents all data values in a format that allows one to get a sense of
the distribution’s shape. In that sense, its function is similar to that of a Histogram, which groups data.
Title
Variable presented and
Leaf size.
These are the stems. The stems represent all
digits of a number except the smallest one. In
this case the stems represent the tens digit as
the measure is in minutes. Here, double
stems are used. The first occurrence of a
stem contains the leaves 0 through 4, and the
second occurrence contains the leaves 5
through 9.
Building a Stem-and-Leaf Plot:
1) Identify the minimum and maximum values to aid
in determining the number of stems.
= 200
122
These are the leaves. Each leaf
represents the ones digit of a
55558
number in the data set. The
00011111122222233334444
number 83 occurs 11 times in
555556666677777888889
this data set.
01112223344
555666777889
012
569
01111111111112222222222222222333333333334444444444
555555555555566666666666777777777777778888888888888888888
00112
556778
1 This number represents 101 minutes.
Frequency
Histogram:
84.5
94.5
Eruptions (min.)
74.5
104.5
Old Faithful: Time Between
100
50
64.5
Minutes Between Eruptions
Now turn this page so that this
arrow faces upward. Compare
the Stem-and-Leaf’s shape to
that of the histogram to the right
.
54.5
4) Add a title, legend noting the size of the leaf units,
the number of values and the variable being plotted.
4
4
5
5
6
6
7
7
8
8
9
9
10
N
44.5
3) The Leaves represent the last digit of the
numbers. Work through the data placing these digits
for all data values to the right of the appropriate
stem. Here the leaves are the ones digit. A time of
95 minutes would be placed in the second “9” stem
(remember the 9’s represent 90).
Stem-and-leaf of Between_Time
Leaf Unit = 1.0
0
2) Decide on Single or Double Stems. If there are
many data points go with a double stem. List the
stems, which represent all but the last digit of the
numbers, in a column.
Number of
observations
OLD FAITHFUL: Time Between Eruptions (min.)