Digits instead of crosses

Stacked dot plots group the values into classes, so some detailed information about the values is lost.

A clever way to retain some of this lost detail replaces each cross with a digit (0 to 9) that shows information about the position of the value within its stack.

Nursing home residents

You are interested in establishing a nursing home for retired people in the USA. Where should it be sited? Information about current nursing home usage in the different states would be useful.

The stacked dot plot below shows the number per 500 population aged 65 or more who are nursing home residents in each state.

Drag with the mouse over the crosses to discover the names of the states.

The crosses only allow you to read off the 'units' digits of the values — Michigan (18.0) and Wyoming (18.9) are on the same stack of crosses. Select Digits from the pop-up menu. The crosses are replaced by the 'tenths' digits of the values.

(Unfortunately neither display directly helps your decision on where to site the new nursing home. Should you pick the state with the lowest number of nursing home residents since there is a lack of facilities? Or would that be the worst choice since elderly people in the state do not seem to like using nursing homes? Further information is needed!)

Stem and leaf plots

A stem and leaf plot is basically a stacked dot plot using digits instead of crosses. However the layout of the display is slightly different.

The layout of a stem and leaf plot makes it particularly easy to read off the values that the leaves represent:

The format is most easily understood with an example.

Software support time

The stem and leaf plot below shows the times (minutes) taken by a software company to respond to 25 telephoned queries about an accounting package that it sells.

Click on any leaf in the plot (a black digit). The corresponding data value is shown above the plot.

Observe that the stem is the 'tens' digit of the value and the leaf is its 'units' digit.