Sum frequency polygon
A cumulative frequency polygon is a graphic representation of a one-dimensional, metric data set.
construction
As with the histogram , the value range of the data is divided into intervals . The relative frequency with which the values lie in this interval is assigned to each interval .
The intervals are entered in a Cartesian coordinate system along the x-axis . At each interval limit , the sum of the relative frequencies of all intervals to the left of the limit is plotted in the y-direction . The resulting points are connected to a line.
Instead of the relative, one could also use the absolute frequencies. This would only change the labeling of the y-axis, but not the shape of the polygon.
properties
- The cumulative frequency polygon is an estimate (approximation) of the cumulative frequency function or empirical distribution function .
- The relationship between a cumulative frequency polygon and a histogram with the same interval limits is as follows: The area of a bar in the histogram corresponds to the increase in the cumulative frequency polygon in this interval.