## Frequency graphs for one quantitative variable

The point is to learn how to "pile up" values that are close together to provide a two-dimensional picture of the data. This is the key idea on which much of the whole discipline of statistics is based.

• Use an individual value plot to remind you of putting points on a number line (from your elementary math classes.)
• Use a dotplot to see how the values "pile up" to form a frequency graph
• Histograms are generalizations of dotplots, where you "pile up" nearby data values by taking intervals of values to make a bar.
• Stemplots are sometimes used as a quick way of organizing the numbers.

More sophisticated choices are available in additional applets. The first applet in each column is the applet described above.

### Stemplot

Instructions/ Discussion of individual value plots

Instructions/ Discussion of dotplots

Instructions/ Discussion of histograms

Watch stemplot and set various options..

Create stemplot and change rounding and splitting stems..

Instructions/ Discussion of stemplots

Boxplots are not frequency graphs in the same sense, because they don't "pile up" the values. They are graphical displays of summary statistics. (For more choices, follow the Instructions / Discussion from the link at the bottom of the applet.)

## Frequency graphs for one categorical variable

Bar graphs

• Vertical axis can be either frequencies or percentages
• The order of the categories (along the horizontal axis) can be changed.
• These differ from histograms in that the vertical bars do not touch each other.

Pie charts (circle graphs)

• Must have ALL values of the categorical variable included so that the percentages sum to 100%.
• Can be labeled with both frequencies of each value and percentages of each value OR just percentages alone.
• The order of the categories can be changed.

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