Statistics - Organizing and Interpreting Data

Frequency Distribution Table

When the range of variable values is wide or the amount of data is large, a stem-and-leaf plot can become cumbersome due to the number of stems and leaves. In such cases, it is useful to organize the data into a format that is easier to interpret.

Here is the data showing the heights of 7th-grade students at Gilbert’s school:

The interval from cm to cm is divided into equal intervals of cm, and the number of students in each interval is counted.

Key Terms

  1. Class: The intervals into which the variable is divided (e.g., ).
  2. Class Width: The size of each interval (e.g., cm).
  3. Frequency: The number of data points in each class.
This table, which organizes data into classes and their corresponding frequencies, is called a frequency distribution table.
The midpoint of each class is referred to as the class mark.

Guidelines for Choosing Class Width

  • Class widths should be equal.
  • The number of classes generally ranges from to , depending on the amount of data.
For instance, using a class width of cm results in fewer classes, making it harder to discern patterns in the data distribution. To capture the characteristics of the data effectively, the choice of class width and number of classes is crucial.