A stemplot (also called a stem-and-leaf plot) gives a quick picture of a set of data, while including the actual numerical values in the graph. Stemplots work best for small sets of data where all values are greater than zero.
To make a stemplot:
1. Separate each observation into a stem consisting of all but the final (rightmost) digit, and a leaf, the final digit. Note: stems may have as many digits as needed, but each leaf contains only a single digit.
2. Write the stems in a vertical column with the smallest at the top, and draw a vertical line to the right of this column. Stems should be in continuous numerical order, so stem numbers without leaves that fall between those with leaves should still be included.
3. Write each leaf in the row to the right of its stem, in increasing order out from the stem.
Consider the following example:
Here is a list of a student's grades on each of 10 biology quizzes:
98, 78, 86, 82, 97, 86, 74, 80, 93, 84
First, write the stems:
7 |
8 |
9 |
Write each leaf on the proper stem, arranging the data in order:
7 | 4 8
8 | 0 2 4 6 6
9 | 3 7 8
You can also compare two related sets of data using a back-to-back stemplot with common stems. Here is a back-to-back stemplot of two students' quiz grades:
Student #1 Student #2
| 5 | 4
| 6 | 0 3 5 7 7 9
8 4 | 7 | 3 7
6 6 4 2 0 | 8 |
8 7 3 | 9 | 9
Student #1's superiority is clear, even though student #2 had the highest quiz score.