Ogive

Data may be expressed using a single line. An ogive (a cumulative line graph) is best used when you want to display the total at any given time. The relative slopes from point to point will indicate greater or lesser increases; for example, a steeper slope means a greater increase than a more gradual slope. An ogive, however, is not the ideal graphic for showing comparisons between categories because it simply combines the values in each category, thus indicating an accumulation (a growing or lessening total). If you simply want to keep track of a total and your individual values are periodically combined, an ogive is an appropriate display.

For example, if you saved $300 in both January and April and $100 in each of February, March, May, and June, an ogive would look like

Figure 1.Ogive of accumulated savings for one year.

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An ogive displays a running total. Although each individual month's savings could be expressed in a bar chart (as shown in Figure 2), you could not easily see the amount of total growth or loss, as you can in an ogive.

Figure 2 .Vertical bar chart of accumulated savings for one year.

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The choice of graphic display, therefore, depends on what information is important for your purposes: percentages (parts of the whole), running total, comparisons of categories, and so forth.