CK-12 Probability and Statistics - Advanced

2.1. Histograms and Frequency Distributions http://www.ck12.org

Take an informal poll of your class. Ask each member of the class, on average, how many beverage bottles they use
in a week. Once you collect this data the first step is to organize it in some way that makes it easier to understand.
A frequency table is a common starting point. Frequency tables simply display each value of the variable, and the
number of occurrences (the frequency) of each of those values. In this example, the variable is the number of plastic
beverage bottles consumed each week. You could use your class data, but let’s use an imaginary class. Here is the
raw data:

6 , 4 , 7 , 7 , 8 , 5 , 3 , 6 , 8 , 6 , 5 , 7 , 7 , 5 , 2 , 6 , 1 , 3 , 5 , 4 , 7 , 4 , 6 , 7 , 6 , 6 , 7 , 5 , 4 , 6 , 5 , 3

Because the data is only limited to the numbers 1 through 8, it is very simple to create a frequency table using those
values. For example, here is a table you could use to collect data from your classmates:

TABLE2.1:

Number of Plastic Beverage Bottles per Week Frequency

1 2 3 4 5 6 7 8

Here are the correct frequencies using the imaginary data presented above:

Figure:Imaginary Class Data on Water Bottle Usage

TABLE2.2: Completed Frequency Table for Water Bottle Data

Number of Plastic

Beverage Bottles

per Week

Frequency

1 1

2 1

3 3

4 4

5 6

6 8

7 7

8 2

While this data set is rather simple and small, you can see how much easier it is to interpret the data in this form.
One caution about translating raw data into a more helpful visual form is that it is very easy to make a mistake,
especially with a larger data set. In this case, it is often helpful to use tally marks as a running total to help construct
the table and avoid missing a value or over-representing another.