How to organize data using
frequency table and stem and leaf plot
Example 1
The marks awarded for an assignment set for a Year
8 class of 20 students were as follows:
6 7
5 7 7
8 7 6
9 7
4 10
6 8 8
9 5 6
4 8
Present this
information in a frequency table.
Solution:
To construct a frequency table, we proceed as
follows:
Step 1:
Construct a table with three columns. The
first column shows what is being arranged in ascending order (i.e. the
marks). The lowest mark is 4. So, start from 4 in the first column
as shown below.
Count the number of tally marks
for each mark and write it in third column.
Example 2
The number of calls from
motorists per day for roadside service was recorded for the month of December
2003. The results were as follows:
Set up a frequency table for this
set of data values.
Solution
Step 1: Construct a table
with three columns, and then write the data groups or class intervals in the
first column. The size of each group is 40. So, the groups will
start at 0, 40, 80, 120, 160 and 200 to include all of the data. Note
that in fact we need 6 groups (1 more than we first thought).
Step 2: Go through the list
of data values. For the first data value in the list, 28, place a tally
mark against the group 039 in the second column. For the second data
value in the list, 122, place a tally mark against the group 120159 in the
second column. For the third data value in the list, 217, place a tally
mark against the group 200239 in the second column.
We continue this process until
all of the data values in the set are tallied.
Step 3: Count the number of
tally marks for each group and write it in the third column.
Do it
yourself:
The data below depicts the amount of time
(in minutes) 20 middle school students spent on the computer each day. Arrange the
data on a frequency table.
10, 32, 8, 55, 5, 0, 30, 20, 25, 45, 40,
60, 45, 15, 5, 56, 47, 12, 15, 20
Number of Minutes on the Computer

Tally

Frequency

0 – 5

I I I

3

6 – 10

I I

2

11 – 15

I I I

3

16 – 20

I I

2

21 – 25

I

1

26 – 30

I

1

31 – 35

I

1

36 – 40

I

1

41 – 45

I I

2

46 – 50

I

1

51 – 55

I

1

56 – 60

I I

2

STEM AND LEAF PLOT
EXAMPLE 1
Complete a stemandleaf plot for the following list of grades on a
recent test:
73, 42,
67, 78, 99, 84, 91, 82, 86, 94
use the tens digits as the stem values and the ones digits as the
leaves. For convenience sake, order the list, but this is not required:
42, 67,
73, 78, 82, 84, 86, 91, 94, 99
Since I know where these data points came from ("a recent
test"), I'll use a title. Then my plot looks like this:
Stem  Leaf 
4 5 6 7 8 9
 2
7 3,8 2,4,6 1,4,9 
Do it yourself now
Complete a stemandleaf plot for the following list of values:
100, 110,
120, 130, 130, 150, 160, 170, 170,
190,
210, 232, 243, 262, 275, 275, 289.
290, 290