http://www.ck12.org Chapter 7. Organizing and Displaying Data
Step 3:Construct the table.
TABLE7.12:
Bin Frequency
[ 20 − 30 ) 3
[ 30 − 40 ) 5
[ 40 − 50 ) 6
[ 50 − 60 ) 8
[ 60 − 70 ) 5
[ 70 − 80 ) 3Step 4:Determine the sum of the frequency column to ensure that all the data has been grouped.
3 + 5 + 6 + 8 + 5 + 3 = 30
When data is grouped in a frequency distribution table, the actual data values are lost. The table indicates how many
values are in each group, but it doesn’t show the actual values.
There are many different ways to create a distribution table and many different distribution tables that can be created.
However, for the purpose of constructing a histogram, the method shown works very well, and it is not difficult to
complete.
Example B
The numbers of years of service for 75 teachers in a small town are listed below:
1 , 6 , 11 , 26 , 21 , 18 , 2 , 5 , 27 , 33 , 7 , 15 , 22 , 30 , 8
31 , 5 , 25 , 20 , 19 , 4 , 9 , 19 , 34 , 3 , 16 , 23 , 31 , 10 , 4
2 , 31 , 26 , 19 , 3 , 12 , 14 , 28 , 32 , 1 , 17 , 24 , 34 , 16 , 1 ,
18 , 29 , 10 , 12 , 30 , 13 , 7 , 8 , 27 , 3 , 11 , 26 , 33 , 29 , 20
7 , 21 , 11 , 19 , 35 , 16 , 5 , 2 , 19 , 24 , 13 , 14 , 28 , 10 , 31
Using the above data, construct a frequency distribution table with a bin size of 5.
Range: 35− 1 = 34
34
5= 6. 8 ≈ 7
You will have 7 bins.
When the number of data values is very large, another column is often inserted in the distribution table. This column
is a tally column, and it is used to account for the number of values within a bin. A tally column facilitates the
creation of the distribution table and usually allows the task to be completed more quickly. For each value that is
in a bin, draw a stroke in the Tally column. To make counting the strokes easier, draw 4 strokes and cross them out
with the fifth stroke. This process bundles the strokes in groups of 5, and the frequency can be readily determined.