Basic Statistics

NUMERICAL METHODS OF ORGANIZING DATA 37

Table 4.2

Workers (g/cm3)

Ordered Array of Hemoglobin Levels of 90 High-Altitude Mine

12.2 16.4 17.8 18.4 19.0 19.5 20.0 20.9 23.0

13.1 16.8 17.8 18.4 19.1 19.5 20.0 20.9 23.0

14.3 16.9 17.8 18.4 19.1 19.7 20.2 21.0 23.2

15.5 17.1 17.8 18.4 19.2 19.7 20.3 21.1 23.3

15.5 17.2 18.0 18.5 19.2 19.7 20.3 21.4 23.5

15.6 17.3 18.1 18.5 19.3 19.7 20.5 21.6 23.5

15.9 17.4 18.2 18.5 19.3 19.7 20.6 21.7 24.1

16.1 17.6 18.3 18.5 19.4 19.8 20.6 22.0 24.2

16.2 17.8 18.3 18.8 19.4 19.9 20.8 22.4 24.8

16.2 17.8 18.3 19.0 19.5 19.9 20.8 22.7 26.2

Table 4.3 Stem and Leaf Table of Hemoglobin Data

First Two Digits Third Digit Count Cumulative

12

13

14

15

16

17

18

19

20

21

22

23

24

26

2

1

3

5659

842 192

48832868818

554353483140425

970322458154977175730

236089568903

76410

740

320505

128

2

1

1

1

4

6

11

15

21

12

5

3

6

3

1

1

2

3

7

13

24

39

60

72

77

80

86

89

90

are 12 and the leaf is 2. Note that 12, 13, and 14 occur only once but 15 occurs four
times.
From the stem and leaf table the investigator can look at the numerical values in
the data and get an impression of how the data are distributed. From Table 4.3 one can
see that the most common hemoglobin level is 19 plus and that there are more values
< 19.0 than > 19.9. Stem and leaf tables are also useful in seeing whether the person
who takes the data tended to round the numbers to whole numbers or halves. This
would show up as an excess of 0’s and 5’s in the leaf column. Stem and leaf tables
display both graphical information on the shape of the distribution and numerical
values of the observations.
If we had four digits, we could call the first three the stem and the last one the
leaf, but that would result in a long table, so perhaps a better choice would to call the
first two digits the stem and the last two the leaf. The stem and leaf table is easy to