Frequency Distribution

Frequency distribution graphs present all the actual data for a single variable. Their purpose is to illustrate the shape and distribution of the data, making it easier to identify outliers, gaps, clusters, and the most common data points.

Stem-and-leaf plots are examples of frequency distributions. Each number in the data set is divided into a stem and a leaf. The stem consists of the first digit or digits, and the leaf consists of the last digit. The stem can have any number of digits, but the leaf will contain only one number. For example, the number 1004 would be broken down into 100 (stem) and 4 (leaf), and the number 1.9 would be broken down into 1 (stem) and 9 (leaf).

Table 1 is a stem-and-leaf plot of grades in a history course. The graph was created using Word (a vertical bar was typed on each line). The plot illustrates that there are 21 grades, one grade of 39, none in the 40s, one grade of 57, two of 63, one of 64, one of 65, one of 67, three of 70, and so on.

To create a stem-and-leaf plot, follow these steps: 1. Put all the raw data in numerical order.

1.
Put all the raw data in numerical order.
2.
Separate each number into a stem and a leaf.