Ogive
An ogive (pronounced o-jive) is a cumulative frequency polygon. An ogive is the curve of a cumulative distribution function. Similar to Frequency Polygon, construction begins with the Class Endpoints along the x axis and the Frequency along the y axis.
The use of cumulative frequency values requires that the scale along the y axis be great enough to include the frequency total. A dot of zero frequency is plotted at the beginning of the first class and construction proceeds by marking a dot at the end of each class interval for the cumulative value. Connecting the dots then completes the ogive.
If you want to describe the number of data entries that are above or below a certain value, then you can easily do so by constructing a cumulative frequency graph.
An ogive is a line graph that displays the cumulative frequency of each class at its upper class boundary. The upper- boundaries (Class Endpoints) are marked on the horizontal or x axis and the cumulative frequencies are marked on the vertical or y axis.
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 and thus indicates 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.[1]
An ogive displays a running total.
Constructing an Ogive (Cumulative Frequency Graph)[2]
- Construct a frequency distribution that includes
cumulative frequencies as one of the columns.
- Specify the horizontal and vertical scales. The horizontal
scale consists of upper class boundaries (Class Endpoints) and the
vertical scale measures cumulative frequencies.
- Plot points that represent the upper class boundaries and
their corresponding cumulative frequencies.
- Connect the points in order from left to right.
- The graph should start at the lower boundary of the first class (cumulative frequency is zero) and should end at the upper boundary of the last class (cumulative frequency is equal to the sample size).
