Stem-and-Leaf
overviews     see also 

Graph > Stem-and-Leaf

Use to examine the shape and spread of sample data. Minitab displays a stem-and-leaf plot in the Session window. The plot is similar to a histogram on its side, however, instead of bars, digits from the actual data values indicate the frequency of each bin (row).

Below is a stem-and-leaf plot for a data set with the following five values: 3, 4, 8, 8, and 10.

Stem-and-leaf of C1  N  = 5

Leaf Unit = 1.0

 1   0  3

 2   0  4

 2   0

(2)  0  88

 1   1  0

The display has three columns:

·    The leaves (right) - Each value in the leaf column represents a digit from one observation. The "leaf unit" (declared above the plot) specifies which digit is used. In the example, the leaf unit is 1.0. Thus, the leaf value for an observation of 8 is 8 while the leaf value for an observation of 10 is 0.

·    The stem (middle) - The stem value represents the digit immediately to the left of the leaf digit. In the example, the stem value of 0 indicates that the leaves in that row are from observations with values greater than or equal to zero, but less than 10. The stem value of 1 indicates observations greater than or equal to 10, but less than 20.

·    Counts (left) - If the median value for the sample is included in a row, the count for that row is enclosed in parentheses. The values for rows above and below the median are cumulative. The count for a row above the median represents the total count for that row and the rows above it. The value for a row below the median represents the total count for that row and the rows below it.

In the example, the median for the sample is 8, so the count for the fourth row is enclosed in parentheses. The count for the second row represents the total number of observations in the first two rows.

Dialog box items

Graph Variables: Enter one or more columns of data. Minitab displays a separate plot for each column.

By variable: Enter a column containing a grouping variable. The values in the By variable column must be integers between -10000 and +10000 or the missing data symbol (*). Minitab produces a separate plot for each group. This option does not work with the Trim outliers option.

Trim outliers: Check to trim all outliers and show them on special lines labeled LO and HI. This option does not work with the By variable option.

Increment: Enter a number to control vertical scaling by setting the increment between display lines (the difference between the smallest possible values on adjacent lines).