The Essentials of Biostatistics for Physicians, Nurses, and Clinicians

38 CHAPTER 3 Graphics and Summary Statistics

3.4 STEM - AND - LEAF DIAGRAMS

John Tukey devised a quick way to summarize the data in a similar
way to a histogram but still preserving all the individual data points.
He called it a stem - and - leaf diagram because it looks like a stem with
the individual points protruding out like leaves on a tree branch.
We see from Table 3.4 that the leaves produce the shape of the
histogram on its side. This is a little different, because we chose 21
equally spaced intervals instead of 7 so that the stem could be the fi rst

Table 3.4
Stem - and - Leaf Diagram for BMI Data

Stems
(intervals)

Leaves

(observations)

Frequency

18.0 – 18.9 3 1
19.0 – 19.9 28 2
20.0 – 20.9 278 3
21.0 – 21.9 111335999 9
22.0 – 22.9 333457789 9
23.0 – 23.9 011345 6
24.0 – 24.9 000112335667788 15
25.0 – 25.9 04446778899 11
26.0 – 26.9 255569 6
27.0 – 27.9 1333344444556 13
28.0 – 28.9 233346778889 12
29.0 – 29.9 358 3

30.0 – 30.9 01238899 8
31.0 – 31.9 01366 5
32.0 – 32.9 68 2
33.0 – 33.9 26 2
34.0 – 34.9 289 3
35.0 – 35.9 0589 4
36.0 – 36.9 6 1
37.0 – 37.9 158 3
38.0 – 38.9 28 2
Total — 120