Quantitative data charts, also called grouped data, can be viewed using a histogram or a polygon.
How to graph quantitative data
 Place the classes on the horizontal axis
 You can place either the frequency distribution, the relative frequency, or the percentage on the vertical axis.
In the lesson on creating a frequency distribution, we ended with this table showing the frequency distribution, relative frequency, and percentage distribution.
Let’s use a histogram and a polygon to display the data. There is little difference between the two charts except that the histogram uses rectangles and the polygon uses points.
In both cases we will use the frequency distribution to build the graphs.
histogram
First, put the classes on the horizontal axis. Second, put the frequencies on the vertical axis.
Finally, draw a rectangle for each class so that the height of the rectangle corresponds to the frequency of that class.
Notice that all the rectangles are adjacent and, unlike a bar graph, have no gaps between them.
Notice that the numbers from 0 to 8 do not appear on the horizontal axis.
Also notice that immediately before the first rectangle on the left there are two small parallel lines that make the horizontal axis discontinuous.
We call this an interruption or a cut off in the axis. Whenever some numbers on the horizontal or xaxis don’t show up, we will cut off the xaxis.
That histogram above is called a Frequency histogram.
If you had used relative frequency to build the histogram, you would call the chart a Relative Frequency Histogram.
If you had used the percentage to build the histogram, you would call the chart a percentage histogram.
Polygon
Simply use points instead of rectangles to draw a polygon.
Place a point just above the midpoint of each class.
The height of the point should correspond to the frequency of this class.
Create 2 more classes. The first is created before 918 and the second after 5968. Both classes have a frequency of 0.
Connect all points with straight lines.
Notice that this time we didn’t cut off the xaxis as it uses all of the values on the xaxis.
The above diagram is called a frequency polygon or simply a polygon.
If you had used relative frequency to create the polygon, you would name the graph a Relative frequency polygon.
If you had used the percentage to build the histogram, you would call the chart a Percent polygon.

Quantitative data charts
May 18, 9 p.m., 6:54 a.m.
Quantitative data charts, also called grouped data, can be viewed using a histogram or a polygon. Learn how to create histograms with raw data
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