Frequency Polygons

data presentation

Frequency polygons are a common form of chart used in data presentation. Frequencies are plotted on the graph as points (or crosses etc.) and joined up by straight lines. They are called frequency polygons because polygons are shapes where the vertices are joined up by straight lines. However, the first and final points are not joined up so it should be thought of as more of an open shape.

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Cumulative Frequency Diagrams

data presentation

Cumulative is the adjective for accumulate. It means to add up successively. It follows that cumulative frequency is where the frequencies are added up at each step.
The lower quartile, the median and the upper quartile can be identified from a cumulative frequency diagram.

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