Frequency Distributions

A frequency distribution table summarizes the number of times that objects, classes, or numbers show up in a data set

The main parts of a frequency distribution table are...

A CLASS which refers to a particular range of values
CLASS WIDTH refers to how big this range is
- Class widths are typically established by using:

CLASS BOUNDARIES are the value that separate classes

CLASS MIDPOINT refers to the halfway point of a class
- The Midpoint is found by using

Steps for Creating a Frequency Distribution Table

Calculate class width and round if necessary
Set up classes using the calculated class width and count the frequency of each class

Example: Create a frequency distribution table with 5 classes for the following data set

56, 52, 50, 52, 59, 54, 58, 59, 57, 56, 51, 53, 52, 55, 54, 51, 59, 56, 56, 52

Calculate class width and round if necessary

We can round 1.8 to 2 in order to make it easier to establish the classes.

2. Set up classes using the calculated class width and count the frequency of each class

Your starting point will depend on your data set and your discretion. You don’t necessarily have to begin at a round number but doing so will make it easier to establish the following classes.

For this example, we begin at 50 and add the class width of 2 to get the starting point of the following class

The ending point of each class is (the beginning of the next class – 1). For example, the ending point of the first class in this example is (52 – 1) = 51

Repeat the process until you have 5 classes

It helps to sort your data from smallest to largest